Why does he take his shirt off and show it off?

There's this guy (neighbour) on warm days he walks with no shirt. Then he has his curtains open and you can see him walk like that, and I have the curtains open, when I wait for packages but then he sees me looking and then he smiles and closes the curtains.

Yesterday he did his door open while he had no shirt on and try to fix something but he was just touching his door, like he did nothing.
He keeps doing that. While my friend notice it too but also notices he stares at me sometimes.
But he is not my type at all. When he stares too long and I see it, I quickly look away so he won't get any thoughts as if I like him.

It's like he wants others to stare at him.
Why does he take his shirt off and show it off?
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