Rhythmic stimming

Hi, I dont post a lot here, but feel I need to find out as much as a I can. I have medical and health anxiety along with other mental health issues. 4 years ago my eldest son developed a tremor type tapping in fingers.

He went to the Gp and I did all my research on jerky tapping tremor type movements. I dont think he followed up with the Gp and let it go, I’m not sure what they said.

I did see in my research,that benign fasciculation is caused by stress or virus. It settled for him and I think stress can flare it.

He is a supervisor in large mining company in Indonesia and he will do 3 weeks. of day shift and then 3 weeks of night shift with only one day off per week and after 8 weeks have 4 weeks off. He wakes at 3 am to go to day shift. He travels 2 days to get there.

He is not worried about the tremors, he calls it stimming to overwhelming sounds.
When he gets in the mine, with multiple bigs loud noise, trucks, machinery etc. His fingers want to start tapping. He said when he hears music, he is covered in goosebumps and want to dance and move. Is this like restless leg syndrome or too much stimuli. He has looked up rhythmic stimming.

I dont know where to start to find out.. Has anyone on this forum heard of rhythmic stimming, and what is it? I’m a mother out of my anxious mind.

I know about stimming with autism, my daughter is on the spectrum and her stims come from too much public stress or excitement.

Please dont scare me, but I would like to know. MND scares me, my brother in law died of it.

Thankyou for this forum and any support/advice.