My daughter has a good friend that does this when she creating fantastic stories in her head or she gets otherwise very excited. Her daddy is PG for sure. The school caught the arm flapping at first grade and sent her for an eval in autism clinic and nothing was seen that indicated spectrum. She's almost 8 now and it is less. My daughter just started to ask why she does that. A little education and it didn't bother DD at all. Hope that helps a little.