Baby repetitively opening and closing hands

Hi I don't know who to talk to about this but I need some support and help and feel that this is a safe place to ask. I've been worried sick about my 8 month old who has started opening and closing his hands repetitively. He does it mostly when's he's tired or excited so not all the time. He's meeting his milestones and makes eye contact he is social smiles snd babbles. I'm worried his hands are an early sign of autism. He flaps them a littje and kicks his legs but only when he's nursing or taking a bottle at bedtime. One other thing I just read online is about head lag. At 6 months he could not lift his head when being pulled up by his arms from his back I just read online that this could be a sign. He is in the 97th percentile and for his head and low for his weight so I'm hoping that is why he struggled to lift it. He can lift his head now no prob. He growls sometimes too.

My question is... has anyone experienced this with a baby and everything turned out okay? Am I overreacting? is this kinda normal? I've talked with doctor and so far it's too soon to tell. I'm literally sick over it thinking my son could have autism. It's taking a toll on me and consuming my every thoughts. :( any help is appreciated.