[jokermtb]

I rapidly clicked (almost a 'flicking' action) both left and right side steering wheel buttons (the up/down and center buttons) - these might have gotten sticky and was causing the screen to cycle rapidly between multiple settings. Hasn't done it since I shut down and restarted the car with the screen 'off', then I turned on the screen and let it boot up properly. Hopefully it was just dirty steering wheel control buttons. I did also wipe clean the screen at the same time - can't say if that helped or not, but either way, it works as it should now.