Whats wrong with this guy?

There is this guy that has been staring me down in the hallways since the beginning of the year. Its actually creepy, my friends have pointed it out too and asked why he always looks at me. He was once hanging out with my friend and some other people and told my friend he thinks I'm pretty cool yet he has never talked to me. Sometimes when I am walking behind him on my way to class he will turn around, look at me, and turn back around again. He is weirding me out, why does he do this?! And if he does like me why wont he just say something? He never talks to me only stares.