Is it normal to act that way??

Ok well i just got back to school a few months ago and we almost always have new professors every year. However, this year there's something off about one of them. This one professor of which i do not have any classes with or talk to much, hardly ever actually stares at me alot, like ALOT. When this professor gets the chance he comes and talks to me or starts any conversation and at times his eyes wonder off (if u get what i mean) and when he talks to me he stares straight into my eyes, i just feel so nervous. He is a really nice guy but is that normal, i don't understand what he might be thinking? Im confused. I can catch him from far away looking at me, he has no facial expression or anything its just a stare. I think he's noticed that i have noticed so now it happens less but its still there.