Why is he so weird around me?

My colleague is a couple years older than me
(26) and he's pretty confident speaking in our work meetings and stuff but confuses me.
He sometimes won't look me in the eye while talking and will stay looking at his computer.
Once he was looking at his computer and asked me "how's your night going Kacy" and I looked at him and said "good" then I noticed he was smiling and kinda blushing while looking at the computer and then I was like
"why are you laughing?" And he shook his head and said he was looking at something funny on his computer.
Another time we were collaborating on something that we had to work together on and I was about to leave and he was like "Kacy
did you get everything published dude?” And he was smiling and looking at his computer And I turned to him and was like “yeah I think so” and he was still looking at his computer smiling and was like “thanks for your help today” and i said you’re welcome and it got awkward so I left a few minutes early. Another time the guys were playing desk basketball and he was like “Kacy make sure you’re watching this” and tried to shoot the basketball in the hoop. He missed and after was like “Kacy i’m so sorry for missing that"
Like I said he doesn't really talk to me often but has no problem talking to and being obnoxious with his friends at work.
A while ago he was ranting about how he hates when one of our colleagues sits next to him and I was like "you like when I sit next you right?" And he kinda smiled and blushed and looked away and was like "it's not even that, it's not even about that" and he kept his rant
up.
When we talk it feels kinda awkward. Like he'll say hi and it feel awkward or nervous energy. The other day I was eating an apple and he stood up from his computer while watching a football game and was like “Kacy this game is annoying” and I said sorry because I was mid bite when he said that and smiled and he awkwardly smiled too and said “it’s all good”. Could I make him uncomfortable?
Why is he so weird around me?
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