I don't think that is the cause of his stimming, never know and I could be wrong! But most often, stimming (such as hand flapping) is a way for them to sort of self regulate their senses. As most children with autism, regardless of where they are on the spectrum, have some sort of sensory issue (Most often Sensory Processing/Integration Disorder), to some degree, they find various ways to regulate what they are taking in. This is then out put, in various tics or stimming. It's something they have control over and allows them to sort of de-stress and reduce anxiety. My son twirls his hair into knots or kicks his legs very rhythmically and tends to do it more in newer environments, overcrowded places or when he has had too much (sensory stimulation) for the day.

I've also noticed that before a meltdown, he often does these things in a much more crude way, like he's trying to fix a problem and just can't.

I haven't been on here for a while so I am trying to catch up so bear with me. I posted an answer to one of your most recent questions and want to a a comment here.

It was nice when my son got older and became aware enough to be able to answer me. I had been asking doctors, other professionals and other parents for years why he did these things. His was mostly almost constant rocking both standing and sitting although he did some other things periodically. I finally was able to go to the source and ask him. "Why do you rock? How does it help you?" For me his answer simple and enlightening. No more guesses from others or myself. He said "It just makes me feel like I'm not floating." So his reason was basically sensory.

But in the mean time I had to adapt. He needed to do whatever it was and even if I didn't know why, I did know he needed it. I am not the one with autism so I was the one who needed to come up with a solution we could both live with...after he rocked the back out of two sofas, broke three rocking chairs and snapped the steal in the front seat of my truck (that was unbelievable).

So for me I follow the "what can I figure out that makes this tolerable for me!" so I can focus more on how to help him without loosing my mind and fussing and yelling at him! It saved my sanity at least. Or at least I think it did? I may have lost it and just not have realized it yet! Haha.

Just a little story if you want to read it.
As his mom I had no idea the skills he was teaching me until I was substituting and a student in a regular class had the clipboard with the student's names. When I asked for it, he told me no but not with any disrespect. Because of my own son I recognized that he "needed" that clipboard for some reason. It didn't really matter why. I just needed the attendance list. I tried four different options before I got an "OK" from him. I've learned to think outside of the box and respect the needs of others even if I don't understand it.

Hand flapping us a self regulating behavior, unless the child causes self harm. It is a sensory need which emerges from being over stimulated it being stressed. Stopping the behavior causes more issues. Instead redirect to something that is calming to the child.

My son has recently started stopping all over the house ( unbelievably annoying) asked his OT she said looking for sensory input try joint compression on his knees and ankles I do two or three to each leg and he feels better for awhile and the stopping stops. Some stims there are other ways to find some relief, others like the scripting I guess he just needs to do it

agree with statement from JKatSchultz. Its all about regulating their emotions. Can come out in various ways with increased or decreased regularity or intensity. Our son had quite a few stims when younger (hand flapping a lot, hopping up and down, grunting, etc..). All would come out more particularly when he was excited. Even now, while he's lost many of them, if he's playing a video game he needs to stand up and walk around the whole room while playing......and will hop up and down when he does something in the game. Its more or less a relief vent for all of his pent up excitement. What we've tried to do (limited success) over the years is redirect his stimming away from things that would be socially disruptive (like hand flapping) to ones that are as effective but more socially acceptable (like squeezing his hands together or using a fidget toy). Just so that he does not disrupt school classes. What I have noticed now as he turns 7 is less things like flapping and new stims like biting on his fingernails. What we have learned is any attempts to stop the behavior ill likely be unsuccessful as it is his way of regulating himself