common problems on em, my sisters had the same issue, but thankfully she had full history so Vauxhall sorted it.

you can ask for a CIM update (i believe that's what its called) which does fix alot of strange electrical issues.

other problems can be the loom to the ecu or the ecu itself.

my sisters problems started with the radio coming on when they were asleep in the house!, the key fob not unlocking the doors, and latterly the engine not starting as the immobilizer would not go off.