I've experienced this since age 10.
When trying to hold eye contact for more than a second or eat in front of people I didn't know, I would have head tremors, called, I believe, "essential tremors," which others have described as quivering in a way that seems to be tiny "no" head shakes.
Have come to realize recently that many people suffer from this.
It can be horrible.
One thing I learned helped was consciously relaxing my shoulders when I expected this to occur. I realized my shoulders would tense and rise when I was anxious.
Another thing was realizing that having it happen didn't make people shun me. It didn't affect friendships and I had many girlfriends in spite of this before marrying.
It still happens from time to time, but the frequency has lessened.
Hang in there and don't let this stop you from living your life.
You're not alone.