Reassurance

My son is just shy of 7 months old and the past few weeks he’s started shaking his head on and off (kind of like saying no) but he does it, I’ll say medium speed. It doesn’t seem involuntary because if I touch him or distract him while he is doing it he stops. Is this just for fun?

I am pretty confident this is normal/common from what I read but just looking for reassurance. Plan on checking with the doctor at his next appt too.