DS2 is 7mo and is a very fidgety, curious, strong baby, constantly moving. He loves to kick his legs and his arms and legs are always pumping and reaching and grabbing etc
Recently I've noticed he's doing this thing with both hands where he's making twisting, waving, scooping movements. Other times it's like he's playing the piano, wiggling his fingers up and down. He does it basically all the time when he's not using hands for anything else. It's very fast when he does it.
I know you posted this a while ago, but just wanted to say my daughter did this too around that age, still does sometimes. She just seems to move her hands around in circular motions and like you said it's waving and scooping motions. I think it's normal?