TV switches to standby after 5 seconds - any ideas?

[nb3tre]

Our Sony Bravia W40A12U has suddenly started to switch itself to stand-by mode after only 5 seconds. Has anyone seen this before - any ideas please?

[Bravia55HX]

Hi,

does the red standby light blink a number of times in intervals?, if so its a fault that requires a service technician to look at.