Why do guys avoid eye contact?

So I've noticed him looking at me from a distance a few times, but up close when I look at him, he completely avoids me. I can't say I haven't done the same, sometimes I look down and keep walking and avoid eye contact because I like him so much.

Today in class I looked up at him when he was in front of me and he kept averting his eyes. I looked up again just to see if he was still looking, and his eyes shifted really quickly. Why?
Why do guys avoid eye contact?
Add Opinion