Colleague pushing my buttons. What does he want? Always Hot and cold and colder then hot again?

He is nice once in a while and then when I am actually being friendly, warming up to him, he simply becomes mean/ignoring work texts, not answering emails/keeping important work information all the while being extra helpful to other female colleagues in front of me (the same day). I have confronted him about the issue but he simply refused to even acknowledge any problem between us. With a nice little comment: you take things too personally. As he is senior to me, I often have to work with him so can't escape him. I have also noticed him staring at me and checking me out but after that simply nothing or he simply tried to push my buttons in work context (examples above) knowing full well that I hate this behavior. Since, he is married, l have no reason to think that there is any actual interest from his side. But I never understand why would someone intentionally irritate someone else, try to get a reaction.

Colleague pushing my buttons. What does he want? Always Hot and cold and colder then hot again?
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