Why is it so difficult to start talking to him?

I have a crush on someone. The problem is we don't really talk to each other. We go to the same school but we only have a single class together in which he sits in front of me.
I don't know how to start a conversation without appearing creepy or just coming out of nowhere. The only thing I am sure that we have in common is that we both play a videogame (League). I wanted to go on ts with him or something like that but lately he doesn't come online anymore. So there goes my plan.
My question now is how do I start talking to him? I don't want to appear needy or annoy him.
Btw, I once tried talking to him. We had to wait together in a room where we were alone. But things were just awkward. I askes some questions to which he only replied very shortly and in the end I stopped talking because I didn't know what else to say. We had to wait there for 50 minutes Q.Q 50 minutes of awkwardness.