Today whilst walking passed the TV (Samsung Plasma) I heard a loud click, the same noise as when I turn it on using the remote ... doesn't turn on though.

Mentioned this to my wife who said that it often happens during the day, not sure why this is the first time I have noticed it happening ... blind and deaf probably 

Whilst typing this, I heard it again, and thinking someone had turned it on, took a look and nothing!

Are there heat/temperature sensors that cut out standby power, or ghosts in the machine? 

PS  No off/on timers are set.