PLEASE HELP - Philips - 32PFL5522D TV - No picture

[clicketyclix]

Hello

When I turn the TV on a multi-coloured picture is on the screen but the sound is normal, then, after half an hour or so the picture turns completely back to normal and the TV is in perfect working order.

I'm hoping it's a cheap fix as it's not under warranty.

Any help greatly appreciated

Raff