As a person that could always talk to people, I suppose I can't say much from your point of view.. But I think it's just because you're not used to talking to people. Your body might feel differently about it than you yourself will. Honestly, I was always bad at talking to people until- this might sound odd but- I started majoring in English, which helped me put together my words properally. (Yet, I still don't speak as well to people in voice, but it's decent enough..) Personally, I still don't know what to do, how to approach, or what to say. I wait for people to approach me, instead. If they start something, I'll continue it. I don't enjoy doing it any other way, because I'm scared I'll say the wrong thing. But again, I think the not being able to talk to people is your social anxiety, or you just not being used to it at all. You should find someone who's close to you and talk to them, or anyone. Just get the hang of talking and all, I think that's a good first step for you to do.