What does Brutus fear in Act I, Scene 2 of Julius Caesar?

In Act I, Scene 2, Brutus is uneasy with himself; he fears his misgivings and some inner conflicts that he experiences. He says he is "with himself at war" (1.2.48).

Stronger than all the sterling qualities that Marcus Brutus possesses is his firm belief in and devotion to the principle of republicanism. So, while he is devoted to Caesar as a friend, Brutus is disturbed by Caesar's conduct upon entering the streets of Rome. When Caesar is dismissive of the soothsayer, Brutus fears that Caesar's egotism prevents him for exercising his wisdom. Moreover, Brutus is worried Caesar may become king now that Pompey has died and Caesar is the only remaining member of the triumvirate. 

Indeed, Brutus is very troubled by Caesar's rise to power after the death of Pompey. Valuing honor above all else, Brutus fears Caesar may be made king by the people and become tyrannical. He tells Cassius that he would rather be "a villager" than to call himself a son of Rome under a dictatorial leadership:

Brutus had rather be a villager

Than to repute himself a son of Rome

Under these hard conditions as this time

Is like to lay upon us. (2.1.173-176)