I have the same exact experience as you. It's like some weird physical barrier, but I can't really articulate the feeling or explain it. The exposure therapy method here doesn't work because "just do it a bunch of times and you'll get more comfortable" isn't even possible for me, I can't "just do it."

For me though, it takes more than a few beers to be comfortable approaching someone. I'd have to be completely sloshed and even then it's a struggle.

The only time I didn't experience the seemingly physical barrier was in college when a friend convinced me to try MDMA and we went out. I became almost the exact opposite of who I am with the social anxiety. I was the most extraverted, outgoing person in our group quite literally chatting up anyone and everyone that I crossed paths with without any care or inhibition around it.

No other pharmaceutical has been able to cure it for me like that, and it's a bit depressing because I liked that version of myself and I'd like to be able to be that person again without an incredibly dangerous illegal substance.