Recently noticed that when I start the car the 512GW runs for about a minute then switches off for another minute or two then back on again when it works fine for the remainder of the journey. This has only started recently and was fine for several months. Its wired through the ignition to the cigarette lighter fuse. Not a big issue at present bit I wondered if it might be a sign of impending doom?. I tried a firmware update but there was none available.