There's a guy at work and I don't know what to make of his behavior. What do you guys think?

I'm a graduate student who works on campus. I've been at my job for 2 years. I always go to the bathroom on a different floor because I don't like the one on my floor. There's a guy about my age who works on that floor. He doesn't know me, but he always say hi when he sees me. Sometimes with a smile. He's been doing that for about as long as I've been at my job. One time he almost hit me with the stairwell door & apologized continuously then struck up a conversation & asked how my break had been. We laughed quite a bit during that conversation & then went our separate ways. Last week, me & this guy almost bumped into each other since I was headed straight & he was going across. We both stopped & then he extended his arm & said "No please, please. I insist" as he let me go first. Yesterday, I was talking to a maintenance guy (who's old enough to be my father so I have no interest in him) in Spanish & shared that I had been at my job all day already by the time he came in. The other younger guy, who also speaks Spanish (but didn't know that I did) intervened & sarcastically but jokingly said "Oh really? What were you doing? Working?" The maintenance guy & I kept talking & at one point we got on the topic of food. The guy was telling me about the foods he likes to eat & as the other guy was going back & forth to another room that he works in, he said "Mmm. That's delicious. I like that too" as he intervened in our conversation again. Why do you guys think he did that? I was thinking that he was doing it for attention kind of like a "Notice me. I'm here too" type of thing, but I don't want to jump to conclusions. Also do you guys think that he's just being nice & friendly or do you think he might be interested? He seems like the friendly/outgoing type.
There's a guy at work and I don't know what to make of his behavior. What do you guys think?
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