Guy's Behavior

Why does a coworker ignore me for months but as soon as he sees me talking with others he wants me to notice him and acts nice?

He ignores me most of the time and was always aloof and uninterested when I approached him with work related questions but later complained to my boss about me being too quiet and not forward enough. Most of the time I felt like he wanted to get rid of me even though he was really not that busy and always had time to flirt or sneak off with his work wife for hours of take 2 hour coffee breaks with friends. With EVERYONE besides me he is very charming, curious and extremely polite. Now whenever he sees me talking to anyone else he stands up and wants me to notice him. One time he came up to me after he heard me chatting with a new coworker and offered me to walk around the site. While he talked to me he was acting weird and looking at the ground or at his laptop the entire time as if he felt uncomfortable or guilty about something. What is this dudes problem? Like I'm not cool enough to be friendly with until some random dude he doesn't know gives me his approval? Am I that ugly?

Why does a coworker ignore me for months but as soon as he sees me talking with others he wants me to notice him and acts nice?
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