In Hamlet's third soliloquy (II. ii. 526-582), he complains that he hasn't acted on his need for revenge. Why hasn't he? (526-577)
Concerning Shakespeare's Hamlet and your question about Hamlet's delay, you give two different sets of line numbers, neither one of which fits with Act II:ii. I'll go with the soliloquy itself.
In this soliloquy Hamlet has been shamed by the powerful emotion the actor was able to evoke, when he was only acting. Hamlet feels rebuked.
He tells the audience exactly why he hasn't acted and achieved revenge yet, though. The information is at the close of the speech/scene.
...The spirit that I have seen
May be a devil, and the devil hath power
T' assume a pleasing shape, yea, and perhaps
Out of my weakness and my melancholy,
As he is very potent with such spirits,
Abuses me to damn me. I'll have grounds
More relative than this. The play's the thing
Wherein I'll catch the conscience of the king.
The fear of being deceived by a spirit was a real fear in Shakespeare's day, or, if not, was at the least an expected convention of Elizabethan drama/tragedy. Macbeth, after all, was deceived by witches in a similar way.
Hamlet does not appear to be a coward. Notice how he reacts at the graveyard when he charges Laertes, and how he reacts when his mother is poisoned. Hamlet is depressed and suicidal, as well. He's not even sure existence is worthwhile. He's not afraid of death. In his anger he spouts rebukes against himself, but his answer is not to be more courageous, but to make sure Claudius is guilty.
Of course, the ambiguity of the play means that there are probably other conclusions one can make as to why Hamlet delays up to this point. It's even possible to see his citing of the question of the ghost's identity as a rationalization and an excuse. But as far as this soliloquy reads, the questionable identity of the ghost is the reason Hamlet delays.
Hamlet's only explanation for why he has yet to kill his uncle to get revenge for his father's death is that he is too much of a coward. He says in this solioloquy simply that he is "pigeon-livered" meaning cowardly. If he were a man, he says, Claudius would already be food for the scavenger birds.
Most critics would say that the real problem is not so much that Hamlet is a coward. They would say that he just does not have a very decisive personality. This is the real problem that he has -- he doesn't have the right personality to be forceful and take revenge.