White screen of death iPod video 30gb gen 5.5

When I turn the iPod on I get a white screen. I re start it by holding the centre and top button down until the apple logo appears (Time varies for this to happen) and when I let go there is a click and the iPod re starts and works fine. Turn off, turn on, works fine. Turn off and leave overnight and when turned on the following day, same problem. I have tried re setting to factory and problem still occurring.

Any ideas please?