When the speaker in Edgar Allan Poe’s “The Raven” hears tapping on his door, he hesitates. Why does he wait before opening the door?

The narrator of the poem is full of sorrow, as he is mourning his "lost Lenore" and attempting to distract himself from these feelings by reading an old "volume of forgotten lore." When he first hears the tapping at his door, he tells himself, half asleep ("nearly napping"), that it is only "'some visitor'" and "'nothing more.'" He mentions, next, that this was in "the bleak December." Midnight, in December especially, is quite dark. December has some of the longest and darkest nights of the year. In general, it is odd to receive a visitor knocking at one's door at midnight. Midnight is hardly a congenial hour to go calling on someone, so it does not strike me as strange that the narrator would be surprised and, perhaps, alarmed by someone at his door at this time of night.
Further, the narrator clearly has a good imagination, as we can see when he says that "each separate dying ember [of the fire] wrought its ghost upon the floor." It's interesting that he chooses the word "ghost" here, especially just before he tells us of his dead lover, Lenore. It seems like he's sort of freaking himself out a bit. At this point, he's woken up a bit more, and he notices the curtains rustling in such a way that, he says, they "Thrilled me—filled me with fantastic terrors never felt before." His heart is beating fast, and he reassures himself, again, that it is only "'some visitor'" and "'nothing more.''
At first, then, the narrator doesn't jump up to get the door because he's dozing off, and it's the middle of the night. Then, however, his imagination takes over, and he becomes fearful of who or what might be there. Finally, his "soul grew stronger," and he leaped up to answer the door, but no one was there.

In Edgar Allan Poe's "The Raven," a man is sitting alone reading when he hears a tapping at his door. He considers that it must be a visitor. However, he doesn't immediately open the door. When regarding why he pauses before opening the door, consider the first line of the poem. The words "midnight dreary" are mentioned, and the man describes himself as "weak and weary." This gives some indication that both the night and the man are dark and melancholy. By noting a "bleak December" and comparing a dying ember of a fire to a ghost, Poe is effectively attaining a mood of darkness and nervous anticipation.
After describing the "sad, uncertain rustling" of curtains, the man admits to being scared. He then mentions twice that it is just a visitor at the door as if he has to talk himself into believing that it is "nothing more." Finally, after delaying because he is scared, the man opens the door to find no one is there.