Is There Something Wrong Here?

I was seeing a guy for a little bit and a friend who knows him and myself were talking about things we notice he does which is kind of odd. He could be very normal, alert and witty but there are also times where he completely zones out and will sometimes just give you a blank stare when you talk to him and it takes him a few seconds to reply. He also seems like he is about to say something and then doesn't, like he will look at you and then act like he's going to say something and then stops. He was at my work the other day when I was not there but my friend was, and she was bartending and trying to get his attention to see if he wanted another beer and was literally clapping her hands in front of his face and he was just staring right past her. She had to poke him to get his attention. I noticed these things more when he drank, and when he was really drunk it was very bad. But, there are times when I don't think he had drank that much or at all when he was acting this way. We were thinking a Ritalin addiction, or maybe just a couple drinks interacts with ADD medicine or something? Anyone have a guess?
Is There Something Wrong Here?
Post Opinion