My Bravia has started randomly restarting itself.

It will be fine for a few hours, then it will suddenly cut out, the power light will switch off for about a second (note it doesn't go red like it does when on standby), then the power light will come on, the sony logo will show and it will play the startup noise, then it returns to showing the tv program that was on before. The whole process takes 2-3 seconds.

I'm watching tv using a Humax Foxsat freesat box connected through HDMI, I'm not actually using the tuner built in to the tv.

I'm on the latest firmware and I've tried a factory reset, but all this does is delay the issue. After about a week I'm back to having the restarts happening after a few hours, at which point the restarts happen as much as every 30 seconds.

Does anyone have any suggestions? (as you can imagine this is REALLY annoying!)

The TV is only about 2 years old, it gets used most nights, but I wouldn't say it has been overused. This would be the second fault to have developed since the warrenty ended (the first being a fault with the speakers), quite dissapointed with this TV given Sony's reputation!