My daughter needs stimulation for vestibular processing. So it's her central nervous system not picking up her body being balanced so she uses movement to help her body "sense her balance" with her feet hitting the ground hard with jumping and moving. She gets the full sense of her body balanced and grounded on Earth. Where a typical person just feels balanced everytime we take a step. At times her body isn't processing it.

She used to have a strong need to jump and stem by flapping her arms a lot. Then we got her a small trampoline that helped and her school ordered one that she'd use for her sensory break time. She also used to spin a lot as well. Now she's 10 years old and using dance movements to help her self-regulate. It's so cool...she'll just bust out dancing for a few mins and hopping as she moves then suddenly stops. Sometimes she will let us join in. I freaking love it beause she gets to invite us into her world!

And as for what input is like...its like when you had a bad day and you just NEED that hug...and it feels good to get it...give your little alot of bear hugs...and something you can do when out and about is leg and arm squeezes...take your hand starting at the thigh then squeeze lightly and move down his leg all the way to his feet and toes....do the same with arms starting at the upper arm moving to his hands and fingers.
It gives him tge pressure he needs.
You can also look up queeze vests...pressure shirts...and weighted blankets.
Has a therapist ever mentioned brushing to you?

A month ago I wrote about our experience with the therapressure brush on here which my daughter loved. We’ve since stopped doing it cause it appears I got wrong instructions or maybe I understood it wrong. I believe you only brush a few minutes at a time but I was doing it 30 to 45 minutes and she was falling asleep... weeeelllll... my daughter started drooling a lot more and putting things in her mouth like she did 2 years ago! This started a couple of days after I started the brushing. After discussion with our OT we concluded this could be the reason. we’ve completely backed off for now with plans to start it again the right way in a month or so, things have gotten better since we stopped, just an update. Would hate for this to happen to someone else.

My son needs oral stimulation alot!..he is a sensory seeker!!
We use gum...usually a mint or cinnamon flavored gum....this helps to keep him from putting inedible objects in his mouth...we carry gum with us just about every where we go.
Hope this helps

Cntnd..or a hand drier 10 times LOUDER than us neurotyp's. Or feeling pain more internally like a sore stomach may seem like labour pains. Its good to understand that our kids show signs of both ^.
I hope this helps. Trying to see through eyes that experience everything "differently." Best wishes x.