Guys, Why would he try to avoid me and hide from me?

This guy at work sometimes hides in his seat or under the table when he hears me entering the office and looks the other way. He only smiles at me when other people are around, when we are alone he is very dry and short with me but charming and relaxed with everybody else. After overhearing me complain to another coworker about him ignoring me he approached me to tell me I could always talk to him if I had any work related questions and looked at the ground the entire time as if he felt guilty. What is his problem? He is nice and sociable with pretty much anyone but with me he is very standoffish and avoidant

He thinks your unattractive
Other reason
Select gender and age to cast your vote:
Guys, Why would he try to avoid me and hide from me?
Post Opinion