Is my co-worker flirting or just bening nice?

Okay, I have a question; I start it my new job about a month ago. So far it’s been great my coworkers are nice and helpful. They have been very welcoming. Everything was find until about a week ago, one of my co-workers has started to get more comfortable with me, we been teasing each other back and fort, light flirting. I’m the type of person who puts barriers especially at a workplace, we respect each other, and I really don’t want to misinterpret things. I know he has a girlfriend, which he has never mentioned it. But, for two weeks he has been teasing me, for example, if I’m making copies or working on something on the computer he will call me by my name just to distract me and he smiles or he would just ask a simple question just to get my attention, if I return a document or something else he would manage to get closer to me, he steps into my personal space things like that. I mean I wont denied it he’s an attracted guy, but work is work. I just want to know if he’s just getting to know the person that I am or he has other intention, in which I would take the step to put an end to it the best way possible. Thank you.