Baby shaking like “no”?

My daughter will be 7 months soon, but just recently she started doing this thing where she’s moving her head like she’s trying to say “no”. She sometimes throws her head from side to side while doing it. She’s never angry when she’s doing it as it seems to be more entertainment. She mostly does it when we’re on the floor playing and I have her standing up while holding onto my fingers. She’ll start doing it like she’s saying “no” and usually smiles right after. Randomly, she’ll do it in her bed or in her jumper/walker. The only thing I can find about this online is all the fuss about autism (which isn’t a big deal to me because I believe children are born with it and it develops as the child grows and it is what it is!). Anyone else’s LO doing this?