My son is 3.9, and was diagnosed with HFA about six months ago. He has always sought out vigorous motion and pressure, which used to be lots of hugs (upwards of 50 a day when he was two) but over the last year has slowly become crashing into other people, either with his head or a sort of side slam. He's a bit like the human pinball, and it's becoming more and more pronounced!
I've asked him why he does it, and he can't quite articulate, but he is convinced that he can't stop. He's a self-aware, highly verbal little boy, but his behaviour overall seems much more frustrated these days. The crashing he now does easily 100 times a day, and he has started randomly crashing into strangers.
I've done time outs, redirection, holding him tightly to try and replicate the same sensation, tried to get him to jump on a trampoline etc. but am at a loss. He does occupational therapy twice a week, but it doesn't seem to be helping.