That said, no harm in talking to the HV!
My 8 month old shakes her head at me all the time. If I shake my head at her she laughs and does it back. And the way she moves in her sleep and headbuts the cot I have no clue how she doesn't wake herself up 🤦🏼♀️
My little girl who is now 14 months went through a phase of doing that around 10 months. I also notice she sometimes does it when shes teething. It’s most likely a sensory thing which they will grow out. Try not to worry x
Could well just be trying things out. I remember at my 10 month review asking the hv about my baby shaking her head from side to side. I wasn’t particularly worried, but she was doing it quite a lot. Hv said it’s probably just something she has learned and enjoys doing… in any case, she stopped a few weeks later…