Coworker and personal space?

OK I just started my summer job and there is a guy there that invades my personal space a lot. I don't know how to read him he seems aggravated all the time. This is also my first time working with mostly men. He stares at me but never tries to start talking to me. I hae to answer the phone and he goes out of his way to be next to me and watch me when I'm on the phone in case I have any questions. He doesn't talk a lot but he listens when you wouldn't think he would be another guy was talking to me and he commented on what the guy said to me to my coworker. He is always there when I need help but he seems disgruntled a lot of the time. I always thank him and say I' sorry for bugging him. I just don't know how to read him does he hate me? Does he like me? Should I care? lol I'm just getting mixed messages. : / What do you think?