Why is this guy behaving this way?

This guy always stares when i'm not looking (I catch him from side of my eye). He won't really come into areas where it might be just me and him. He's generally confident and speaks to everyone. He won't call me by my name but if I need help he'll jump to the chance to speak to me or find an excuse about work. He makes it quite obvious when were getting out of work that he's looking at me and has no problem in breaking eye contact when were in the car park. However it's a different story when were on shift together.
Why is this guy behaving this way?
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