How many people remain completely still the entire night and don’t move their heads at all?

Anybody with sleep apnea who has a CPAP has solved a harder version of this problem. It sucks and takes a while to get used to but it's way better than waking up with a headache every day.

I assume that if the implant is helpful the overnight charging will be readily accepted by users.

(I've got a peripheral nerve implant myself so I am quite familiar with what lengths people will go to to relieve pain)