in bartleby, how and why does the narrator begin to question himself?

The relationship between the narrator and Bartleby is an interesting one. For most of the story, as you say, he pities what he perceives to be Bartleby's crazed neurosis. He cannot imagine why Bartleby seems to be so troubled by the ''walls" because they are the source of the safety and stability he loves so much. At the same time, however, Bartleby holds a profound power over the narrator. Even though he "knows" that Bartleby is to be pitied, there is another sense in which he is jealous of who and what he represents.