Originally Posted by Unregistered:
My younger brother, who is on the autism spectrum, used to do a form of this. It was his form of "stemming." When he would get overstimulated, he would shake to release some of the charged energy that he was feeling. An Occupational Therapist would work with him-- using brushing and sensory activities to calm him down.
This would make a lot of sense because she exhibits this the most when she is excited. Overstimulation would really make sense.