Why am I so awkward and clumsy when talking to people?

I (19m) recently started university a month ago, been doing not so bad academically and in group projects too, but when some class mate aproaches to me just to socialize and start a conversation, I always get kinda weird and just don't know how to respond to make a fluid normal conversation, and when I do, I start to like ramble and make cutting responses and in the process I get nervous and make everything tense, then I start to avoid to look in their eyes because of the awkwardness, and in the end, makes the person lose interest in the conversation. I even came to the conclusion that I may have a bit of autism or something. I have like an intern voice in my head that just don't let me stop to overthink everything around me. Just watching all my classmates socializing with one another and having normal conversations makes feel awful. This is really killing meee ;( Need some advices but please don't come with the typical improve your confidence etc. (btw sorry for my bad english.)