Are there resources for learning social skills?

I'm 30 and horrible at keeping friends. I don't know if it's the unschooling or the autism, but I'm told I come across as hostile when I think I'm being nice.

I know the basics. I make eye contact but not too much, I ask people about themselves and their interests to show I'm interested, I don't dominate conversations with myself and my own interests. I try to be a nice person people might want to keep around, too— I give money when someone's in a pinch, I remember birthdays, I help move, et cetera.

Eventually people either people tell me I'm being a dick in ways I never realized, or more likely, they just eventually stop messaging me back.

The one thing I'm sure I struggle with is body language. I've read a lot that you need to mirror the other person's body language, but I don't know how to do that. Especially since I normally meet people at work and we're usually pushing big carts around and moving products and I'm just not thinking about my body as something expressive, just practical.

I'm sure I have many more blind spots that I'm not even aware of.

So like... are there classes for this? Some kind of specialized therapy? I don't really want to try anymore unless I can stop being a dick