Why is he giving out an awkward vibe all of a sudden?

Everyone at my new job is older than me. I’m the youngest person there and I’m the only one there who’s in their early 20s.
I get there first because I’m at the help desk so I’m in charge of turning on music and making sure stuff is in order. Every morning as people come in to work, we always greet each other.
I have one guy who works in the back and cooks and he’s very friendly which I like. He’s very very talented too apparently. Usually on the mornings I get there before everyone else so I’m alone and everyone else walks in one by one.
Today he walked in and came to my desk ( I was alone ) and was like “good morning!” In a really chipper mood. Then he looks at me and is like “I’m really happy to see you today”. And he continued looking at me then I got awkward and said I didn’t know what to say and smiled and he walked away laughing.
Like I said he’s very friendly. Today he came by while I was helping my boss and told my boss he liked her nails in front of me while we were helping each other which was also weird because he had to meet with her several times throughout the day / week in private and could have told her then.
I do sense an awkward vibe between us now. It could seem just like an older guy at work being polite but I think he’s actually closer to my age and can’t be any older than like 32-33.
I ask because I’ve already gotten hit on a couple of times or complimented by men since working at the desk so I wanted to know if he was doing the same. I dressed especially nice so maybe that was it lol. It was nice but the “happy to see you” part seemed kinda flirty.
For some reason after that, things have been kinda awkward around us. This morning I was on the phone with a guy and he came near me and heard everything and I was laughing and stuff while on the phone. After this, we’ve accidentally made eye contact a few times and he seems really short with me or around me and won’t make eye contact with me lol. There’s definitely an awkward vibe. Why?
Why is he giving out an awkward vibe all of a sudden?
Post Opinion