Arm flapping ?

Anona • 3 losses 🌈 👶🏼 1.18.19

My 9mo waved his arm a lot. One at a time like he’s waving hi or bye. Every here and there he’ll do it when someone says hi or bye, but most of the time he does it when he’s excited or upset. Is this normal? I’m a special ed teacher so the fear of autism is strong since I know how common it’s becoming. Anyone else’s baby do this?