why do i feel so irked by some people for no reason?

So, in school or even at home, sometimes I feel annoyed at a person. And this person may be doing something annoying, but the instances I'm talking about is when they aren't really doing anything annoying. They're just talking. Does anyone else relate to that? I really want to know what's going on with me. I felt this way since I was young, but I usually try to keep it to myself since I don't want to be a bitch.