My series 3 has started some weird behaviour. The immobiliser won't turn off at times, leaving me just cranking with no start. I lock / unlock doors which usually gets the engine to start but the behaviour then becomes more frequent and less easily cured until finally, no matter how many times the doors are locked / unlocked, it won't start at all until the battery is disconnected. On reconnection she starts again and for a while the problem disappears. Unfortunately this clears out all the error codes. The dealer mechanics can't figure out what's going on.
They've checked around other workshops but no one seems to have come across the problem. The RAA patrol man said he hasn't come across this either. The dealership now has my car and are driving it around for a few days with the test gear ready but of course, the bloody thing has behaved perfectly so far. The car has just turned 50 000 ks and I want to get this sorted before running out of warranty.
Has anyone come across issues like this with any 380 .. of any series?

I had an issue similar to yours

it was the Battery on its last legs even though it was tested and was given the all clear

new battery sorted it

Thanks. I'll ask them to check it. It's amazing how often simple things like that get ignored. I'll let you know.