I notice when my anxiety starts to kick in my face will start tingling and it gets difficult to make any kind of facial expression, I get stiff, so I'll usually try to massage out where its tingling to get feeling back into that area, I also try to control my breathing. I have never fainted yet, but I imagine when that happens to me I'm bordering on the edge.
My case is that I'm very expressive when it comes to my face. So, when I feel very uncomfortable with something, despite wanting to make a good attempt (smile), I wind up not doing so...
It's annoying, 'cause I only realize either after I've done what I planned to do or I realize after and it's usually obvious 'cause of the other person's face...
“Though I have always made it my practice to be pleasant to everybody, I have not once actually experienced friendship. I have only the most painful recollections of my various acquaintances ..."
― Osamu Dazai, No Longer Human
I used to have this really bad
Awful mouth spasm and would start pulling weird faces to stop it
The only thing that helped me was honestly just pushing through it
Like if i feel a twitch coming on, and I stop (even if im in the middle of a sentence) take a deep breath
And as i exhale i let my jaw go slack
Let all the air go out of my lungs
Breath in and start again
But it is really hard to remember to do this when I so anxious.
But over the past few years
I find myself do it less and less
Even if this doesn't work for you, I think the most important thing is to not let the spasms stop you from talking/interacting
Cause that just reinforces all the anxiety you feel around social stuff