Christ, I thought I might have some tinges of it but after reading this lot it's evident I don't.
Not that I had issues earlier but I've worked behind a till since I was 13, as a result I've spoken to 1000s of everyone from kids to hot girls to shifty looking thief cunts and one time, a murderer fresh from his spree (he seemed nice enough). I can talk to anyone, about anything and it's rare they end the conversation cos I'm a thoughtful and witty bastard, if anything *I* tend to get sick of them and I'm also an opinionated fuck.
I think a huge element of social anxiety is it's origin point, you know some people you merely tolerate and every time you see them approach you go 'Oh gawd' and just hope it's going to be over quickly. Then *you* go and talk someone's ear off past polite tolerance and don't realise it until later and then you've (temporarily) become that same pain in the arse to someone you liked enough to talk that much to.
That thought process kicks off a spiral. Someone makes a sperg of themselves by focusing and dwelling on past social misfires, they compound problems by assuming their next interaction is going to be tainted with croaking, mumbly, stumbly, wobbly un-funny, half thought out ideas and lo and behold that's what happens… it's a self fulfilling prophecy.
That's not to say you should try to plan out what you're going to say that's even more uber spastic and fosters terrible habits that make people sound like either robots or hacky tv hosts. You have to rely on your wits in the moment but they have to be tested to make you a decent conversationalist or storyteller. I'm not saying try to make everything a joke but making people laugh or at least smile as you explain your stance/tell your tale is infinitely preferable to bringing no levity to the table. If you're exuding glum people will cast you like that in their mind when they bother to think of you at all.
Most people give zero fucks unless you're invested in their travails, if you know some of their story and can relate to them with your experiences with some regularity *then* they give a fuck, otherwise you might as well be a cardboard cutout and any sperging you do is a discrete package of data that's readily discarded from their minds.
You should most definitely *consider* what people think of you but never worry about it, all forms of worry are utterly pointless and serve no good purpose.