Nick repeatedly described Tom in terms of Tom's physical bearing, suggesting that Tom is a "brute" on numerous occasions. 

In Tom's first appearance in the story, Nick describes Tom as having "[t]wo shining arrogant eyes" which "established dominance over his face and gave him the appearance of always leaning aggressively forward". Tom's physicality is seen, by Nick, as brutal and cruel, as we see here. These physical characteristics match Tom's behavior as well.

Nick remarks on Tom's infidelities and tells the story of a time when he sees Tom strike Myrtle. This violent bearing is not, however, limited to personality alone but is also linked to Tom's wealth, which insulates him from blame and, it would seem, from moral considerations of any kind. He does not feel any need to be nice to people, as we see in his treatment of his wife and his mistress. He also views his business with Myrtle's husband as a sort of joke, underscoring his lack of empathy and apparent immunity from guilty feelings. (He promises to sell Wilson a car as a pretense for stopping in and making a date with Myrtle. He even brings Nick along to watch.)   

While the link is not entirely direct, Nick's description of Tom's wealth is significantly tied to Tom's overbearing and aggressive stature; his "paternal contempt...even toward people he liked". Coming from an "enormously wealthy" family, Tom is not vulnerable to potential failure as most people are just as he is physically sturdy and built as if from brick.

There is, in all this, a decidedly obtuse aspect to Tom. He is not entirely stupid but he is also largely ignorant (and indifferent) regarding the feelings and lives of others around him. Tom's brutishness is, partly, the result of a lack of caring and the lack of a need to care. It is also partly the result of a lack of intelligence (emotional intelligence at least).

"Completely without taste, culture, or sensitivity" (eNotes), Tom stands as a nearly opposite figure to Gatsby, who remains vulnerable despite his wealth. Both men lack taste and culture, but Gatsby seeks approval where Tom is described as being beyond the need for approval. His family's wealth entitles him to the most unenlightened opinions, which still do not threaten his social position. 

How does Nick describe himself at the beginning of The Great Gatsby?

Nick's description of himself in the beginning focuses on the change that has occurred because of the events in New York. He explains that he comes from a well-known working family, well-off but not extremely wealthy, and that before going to New York, he was a tolerant person to whom people told their secrets.

...after boasting this way of my tolerance, I come to the admission that it has a limit... When I came back from the East last autumn I felt that I wanted the world to be in uniform and at a sort of moral attention forever; I wanted no more riotous excursions with privileged glimpses into the human heart.
(Fitzgerald, The Great Gatsby, mrbye.com)

The events he experienced changed him; he doesn't want to see people's secrets or attend parties, but to live in peace and quiet. He has seen the underbelly of Old Money, with their prejudices and derision for people who work for their money -- as he himself does -- and he is no longer the idealistic young man he was before. He also learns that he has no romantic notions about people and life; he refuses to see Jordan Baker again because he knows that she is not committed to an honest relationship. Essentially, his description is of a young man, just entering mental adulthood, whose innocence has been mostly shattered by the selfish people he has met.

How does Nick describe himself at the beginning of the book The Great Gatsby?

Nick considers himself to have some advantages in comparison to many of the people he has known, in that he possesses "a sense of the fundamental decencies (that) is parcelled out unequally at birth." Because of this inborn reasonableness and ability to remain objective even when others are displaying "many curious natures", Nick has a particular reliability in relating the story of his life, at least in his opinion. Nick feels he is able to avoid judging others; that he is, instead, able to accept people for whatever and whoever they are. He acknowledges faults and shortcomings as well as abilities and achievements, but is not swayed by either, which means he can associate with all types of personalities without being overly influenced by them. "Reserving judgments is a matter of infinite hope."

In the great Gatsby How does Nick describe himself in the beginning of the novel

Nick Carraway spends most of the first three pages of The Great Gatsby describing himself and his background, and then tells the reader how he ended up alone in a house in West Egg one summer. But it is not a physical description; we get no idea of his appearance. While he is clearly going to talk about some past events, we don't know how long ago they occurred. What his self-description does convey is that something transformative has occurred.

Nick's first passage refers to youth and immaturity, to criticism and passing judgment, and to listening to bores. We wonder, then, if the story he is starting will be about judgment or be boring. Since he says he is trying to follow his father's advice, we suspect he did not.

Nick graduated from Yale like his dad and served in the military in Europe in the Great War. "I came back restless." The Mid-west, where he grew up with "advantages," no longer appealed to him. Nick, then seven years out of college, moved to New York. He decides to spend the summer in a "commuting town" rather than the hot city as he starts his new profession as a bond trader. His family seems to have approved of the career choice despite being surprised.

It is not until almost the end of chapter one that Nick tells us that he came East to escape the idea people had that he was engaged.

That information helps to contextualize what he had said on page two about the "intimate relations of young men." After the summer in the East, he says, "I wanted no more riotous excursions with privileged glimpses into the human heart."

That is his set up for introducing Gatsby. It seems the human heart we're going to hear about will not be Nick's.