I think It’s just him exploring his movements , he looks in control of this movements no arms sprawling out or eye roll etc ,, kids do weird and wonderful things don’t they I wouldn’t worry xx
It could be a tired cue. My daughter started doing something similar about 3ish months ago and I thought she had an ear infection at first (still got it checked and no she's fine) and noticed her rubbing her eyes more when she was doing it. Sometimes they do it when they fight sleep
Normal, he either just likes it or does it cus he's figured out he can. He will forget it in a few weeks and move on to the next new thing
My daughter does this too, thought it was just imitating a sneeze 😅