Why is my work manager giving me “flirty”/playful looks and smirks sneakily?

We’re closer in age and worked together a while but flirty has never been the vibe. He was talking himself up about his job position & money, and giving extra attention. Chatting and hanging around more, laughing harder at my jokes. The whole vibe was completely different compared to his usual friendly convos and smiles in passing.
Why is my work manager giving me “flirty”/playful looks and smirks sneakily?
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