Lots of electrical problems, fixed
I used to get...
Vehicle protection system unavailable occasionally on a cold start,
A battery warning light that would extinguish on a restart,
An occasional unexplained flat battery including once while driving
Inertial switch intervened which would stop the car starting
Battery is fine. Earths are all good.
I've just realised that all these gremlins seem to have gone for good since I changed the failing battery cut off switch.
Just posting in case anyone else gets symptons that seem like a weak alternator, failing battery, bad earths or it just seems like your car is possessed and you can't trace it to any conventional source!