In my opinion, you probably like him and you cannot admit it. Once you start shaking when you talk about him, it means you really like him. If you talk to the guy you can tell him that is if you want to go out with him some day.
This used to happen to me too although I'd also feel like I was going tithe throw up. It turned out it was my body's way of telling me not to go for him. Because the first day of school , the first day (our "talking" was over summer last year) all these people were asking me questions cuz he made up a rumor that I made up a rumor that we had sex. So he told everyone not to belive me. It was awful and to this day I do not speak to him..maybe the guy u shake about isn't this bad but just be careful:)
I did this too when I first started talking to my boyfriend. I would uncontrollably shake and he noticed. I just said it was from being around him. It's probably your nerves. That's what it was with me. Your lovestruck.