Is he into me or is he just naturally flirty?

Me and my coworker, this guy at work, always play around and (kinda) flirt. It’s obvious to others, I guess, because we get comments on our relationship. He’ll deny it and always say it’s just our relationship, so I’m not sure if this is an indicator that it’s just his personality? Because he’s very much like this outta work too. It’s only when we’re alone he’s a little more open. Today for example, my coworker was in the other room, it was a slow day, and we were playing around in another room. He was picking me up (arms around waist, scooped me up many times) i was trying to pick him up, we were tickling each other, it was exhausting but fun. Whenever something like this happens, he always looks over to the other room to make sure no one saw, so I have my suspicions that maybe this part of our relationship is something else? I don't know

(Technically a repost because I put a wrong category)
Is he into me or is he just naturally flirty?
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