I do this lots and openly laugh at myself, which tends to mean people either ignore It or join in gently laughing with me. I did get unkind comments when I was younger (up to mid 20s) and had low self esteem and was very embarrassed by it. It says bad things about humanity that no one laughs now I'm not visibly embarrassed by it. Even I can see it's funny at times. Me and my manager sometimes both do it to each other and over the top of each other, which can take quite a bit if unpicking for anyone else there, though we're pretty good at getting each other's intention first time 😂.
It happens most often on the phone for me (because I hate phone conversations so I'm already nervy and jumping ahead in my thoughts). The laughing at myself seems to stop whichever bank, UC, whoever agent becoming brisk and irritated too.
It's definitely impolite to openly laugh at you if you weren't laughing though. Did it seem malicious, or just silly? Try to forget it and not spiral about. It's nothing to feel bad about, they're just a bit unkind and that's no reflection on you.
When I'm aware I'm too excited or worried to make sense (because it's every time my emotions are heightened really, so it's pretty predictable), I try to pause and consider what I want to say almost like an essay point, so I have it unjumbled, if it's important. I always have bullet pointed notes for important phone calls, for things likely to come up. Social situations and chit chat, I just expect people to deal with it and I accept I sometimes make no sense.
DS very successfully had SLT for this issue when he was small though it's definitely something he still actively has to try with, so if it's upsetting you lots, it's worth looking in to. Don't feel bad about it though, there's loads of us like it 💐.