Sony Bravia KDL-40S keeps switching off, flashing standby?

My Sony Bravia has just started switching itself off after 10 - 15 mins. The picture goes off a few seconds before it switches off completely. The standby light then flashes intermittently 4 times - it says I need to contact a sony centre but wondered if anyone else had encountered this and knows what it means. If i swich all power off for a bit I can get it to come back on but only for a little while??