“...She is intentionally nodding to cover up the bobbling ...”
Yes. Hillary is absolutely doing this. For those who didn’t pick up on it - watch again carefully and you can tell when she switches from involuntary head movement to voluntary. It is subtle yet obvious.
This strategy will backfire if she overdoes it because the cover up bobbling will cause her to look ridiculous over time - and then the real involuntary bobbing kicks in as well.
I have seen her nod her head several times when there was no reason to do it - and I haven’t watched her much.