political enemies are certain it's just a matter of time before he crowns himself king.

Ever since driving out the Etruscan king Tarquin the Proud, the Romans have been proud republicans. As such, they are deeply suspicious of anyone who looks like they might harbor kingly pretensions. And although Caesar ostentatiously turned down a mock crown in a grotesque public ceremony, his enemies aren't fooled. They think that was just a piece of street theater.

As Caesar accrues more and more power, showing greater contempt for the traditional political elite, the more it seems that he's hell-bent on making himself king of Rome and turning everyone into his slaves.

That being so, one could say that Caesar is in some ways responsible for his eventual assassination. Had he played the deadly game of Roman politics a little more effectively, then in all likelihood he would've lived to fight another day. But like many men throughout history, his head has been turned by power so much so that he starts to think of himself as untouchable, not so much a king as a god.

Instead of treating the Roman elite with becoming respect—whatever he may have thought about them privately—Caesar effectively ignored them, basing his political power on the plebs. This added fuel to the elite's suspicions that he was prepared to make himself king, and these suspicions had fatal consequences for Caesar.

Caesar is not really portrayed in a bad light in the play. However Shakespeare does stress certain qualities in his character which help to bring about his downfall. From the first he is shown to be quite conceited, grandly speaking of himself in the third person: ‘Caesar is turned to hear’ (I.ii.17)

Generally he behaves as though he were untouchable, far superior to others. This makes him over-complacent in the face of any danger.  For instance, although he does have Cassius’s measure, realising that he is dangerous, he says that he himself ‘is not liable to fear’ (I.ii.198). He dismisses signs and warnings from others, like the soothsayer. He even says, when his wife Calpurnia tells him about her dream that makes her afraid for him, that he is like the stronger of two lions born aas twins:

Danger knows full well

That Caesar is more dangerous than he.

We are two lions littered in one day,

And I the elder and more terrible;

And Caesar shall go forth.(II.ii.44-48)

And, just before his slaying, he appears more self-important than ever praising his own qualities:

I am constant as the northern star;

Of whose true-fixed and resting quality

There is no fellow in the firmament. (III.i.60-62)

This perhaps has the effect of lessening the audience’s sympathy for him somewhat, at the crucial moment of his assassination.

In this play, Caesar is not yet the capricious tyrant that Brutus fears he might become; but his overbearing arrogance and self-conceit, as well as making him a less attractive character, help to bring disaster down upon his head.

It can be argued that Julius Caesar has a role in his own demise because he is too arrogant to listen to the many warnings and his desire for power overcomes his common sense. In arguing this point, it is important to detail the various warnings that Caesar chose to ignore and his reasons for doing so.

Calphurnia tries to keep Caesar home, because she is frightened by nightmares depicting her husband’s brutal death. Her premonition of his murder is so vivid that it should be enough to convince him to stay home. Additionally, she informs him of strange sights that people have reported: a lioness that gave birth in the street, sounds of battle and dying men, blood dripping on the Capitol. Calphurnia will hear nothing of Caesar leaving the house when such unnatural things are happening; she takes them as signs of doom and warns Caesar that such strange events often occur before the deaths of great men. He argues with his wife, telling her,

Cowards die many times before their deaths.
The valiant never taste of death but once.

Caesar refuses to appear afraid, as that would taint his image. His wife is correct when she tells him that his confidence overshadows his wisdom.

Even when the augurers do not find a heart in the sacrificial animal, Caesar explains it away as a test of the gods to see if he is a coward. Caesar egotistically states that he is more dangerous than Danger himself.

While he eventually agrees to stay home to make Calphurnia happy, he quickly changes his mind when Decius promises he will be crowned. Caesar’s greed takes over his better judgement, and he chooses to believe Decius’s explanation of Calphurnia’s dream as a revelation of the good that Caesar will do for Rome instead of the warning that it truly is.

On his way to the Capitol, Caesar chooses to ignore other warnings, because of his quest for power. Caesar ignores the soothsayer who tells him to beware. He mocks the man, saying “The ides of March are come,” meaning nothing has happened to him. The soothsayer knows that the day is not yet over and that Caesar remains in danger, but he can do nothing to convince a man who is driven by desire. Artemidorus begs Caesar to read his letter, which details the names of the conspirators. Yet, Caesar brushes him away, proclaiming that whatever involves Caesar himself should be last in importance. Caesar is attempting to appear selfless in putting everyone else in front of himself; instead, he turns away those who are trying to save his life.

The argument that Caesar is responsible for his own death is made in the play and manages to convince his close friend and "the noblest Roman of them all," Brutus. In its essence, the case against Caesar is as follows. The Roman Republic has existed for five hundred years, after the last king was driven out of Rome. Since then, the Romans have never had a king or any single ruler. The senior government officials are the consuls, and there are two of them precisely because the Romans do not want to place power in the hands of a single man. Julius Caesar, however, is now the leading man in Rome by a long distance. His popularity, exacerbated by demagoguery and personal arrogance, now threatens the security of the greatest nation in the world.

This argument is most convincingly made by Cassius, whose speeches you will certainly want to quote in your essay. However, the fickleness of the Roman mob in the pivotal act 3, scene 2 will also be of use in making this case. They initially seem quite happy for Caesar to have been killed, and they applaud Brutus, until they are swayed in the opposite direction by Antony. Caesar's arrogance is also clear from his own words. In a particularly extreme example, he says to Cassius and Cinna,

Hence! wilt thou lift up Olympus?

When Caesar compares the attempt to alter his decision to lifting up a mountain which is also the home of the gods, Cassius's characterization of him seems justified.

It is an interesting question, and one which I don't think has a straightforward or easy answer. How you address this question would be shaped by how you weigh the various factors that contributed to Caesar's death. Some of these were within Caesar's ability to control, and some of them were not.

First of all, be aware that there existed a conspiracy to bring about Caesar's death. These events were manufactured by outside forces. Furthermore, there is Cassius's manipulations of Brutus himself, using lies and deception to bring Caesar's friend into the conspiracy against Caesar. When answering a question such as this one, you need to account for the fact that Caesar was assassinated. Thus, I don't think you can argue that his death was entirely self-caused. The answer is murkier than that.

On the other hand, however, there are two additional factors to be aware of. First of all, even though Cassius manipulates Brutus to bring him into the conspiracy, the fundamental charge against Caesar—that he is a would-be tyrant—does seem to be valid. Indeed, note that they are able to lure Caesar into the senate with the promise of giving him a crown. Caesar does seem to act out of a desire to dominate the Roman State.

Furthermore, be aware that Caesar is given warning ahead of time, first by the soothsayer in act 1, scene 2, and later by his wife, Calpurnia. Omens play a major role in Julius Caesar, and Caesar himself takes those omens seriously. In act 2, scene 2, Caesar is even temporarily convinced by his wife to remain home that fateful day, though he has a later change of heart. From this perspective, I don't think you can say that he was entirely responsible for his own destruction, given that he was the target of a conspiracy. However, his own mindset, decisions, and desire for power certainly played a role in his demise.