To me random muscles start spasming out of control, often on the face or arms, I can't stop them and it lasts for minutes at times.
The worst is when is visible by others in public, they think "What is he doing?" and look at me weird.
Even got it checked by a doctor and it seems that it's just how my body release stress.
Relaxing music and ASMR helped a lot though. ๐Ÿ˜Ž๐Ÿ‘