Tv turns on with sound but no picture then turns off

Panasonic TX-L32G10B LCD TV

When I turn the TV on there is sound but no picture for a short while and then the sound stops, the red standby light flashes once and the TV turns off.

I have tried turning it off, unplugging it from the wall, holding the power button for 30 seconds and then plugging it back in more than once. When I do this it seems like pressing the power button doesn't work the first time and then it repeats.