I found out about my son at his 12 month checkup when he didn't hit the 12 month milestones. He did flappy hands alot too though. Here is a link for a test to give you an idea of their chances of having it. https://www.autismspeaks.org/screen-your-child
If he's showing empathy and affection then I think you're still on the neurotypical side. It sounds pretty developmentally normal to me, but your pediatrician will tell you more.
My toddler did this exactly. I highly recommend getting his ears checked. He might have extra fluid sitting back there. My 2 yo just recently started to getting ear infections nonstop. He will most likely have to get his adenoids removed and tubes in his ears. He also didn’t show any symptoms of an ear infection, but it was caught during his regular visits.