Can't tell if he interestedor not (this is long)

Ok here's a little background about me-I'm in my early 30's and am coming to the realization over the last year that I'm gay. I'm private person in general and I really don't discuss my personal life. I just go to work, grad school, gym (on weekends), and chill with friends on occasion. I've started online dating and have met up for drinks/coffee with 3 guys that I met online over the last year. I had a good time and remained friends with 2 of the guys that I met.

Here's my situation...I live in Jersey and catch the train into NYC everyday for work and school. I've been doing this for 5 years. On my way home from work I sit towards the front of the train and I usually move to the last car two stops prior to getting off at my stop. About a month ago I notice an older attractive man in his 40s standing in the doorway that I have to walk thru to get last car. I say excuse me to him, he stares at me and moves out of the way so I can get by. A few days go by and I see him again we make eye contact and speak. About a week later, I see him again and this time he pushes the door open for me and introduces himself we exchange names, shake hands and he gives me a pat on the back. I wish him a good night (I never get approached in the street or on the train). We end up having a conversation about school, work, & family two days later and he mentioned that we should talk more and that he's usually on the train M-F. He's not married and doesn't have kids and works in the Financial District. I see him again two days later as I make my way from the front of the train towards that back where he usually sits at. He still spoke and shook my hand but he seemed a little distant and cold. If I asked him a question like how was your weekend he only would give a one word answer. At first I thought nothing of it but it happened two more times.

This situation has me wondering if I somehow offended him. I will admit that I can come off as distant and cold towards people at times but it's only because I usually have a lot on my mind. When this guy approached me I was really caught off guard. When I see him I usually speak maybe ask how his weekend was or he'll say to me have a good weekend with a smile and now he's kinda cold and I feel as if I did something or said something wrong. I've never been approached on the street or the train so this is new to me. If anyone out there could offer some insight it would be greatly appreciated!