We bought a Samsung TV in June.
Ever since it's had a habit of switching itself off at random. When it is switched back on the brightness is up and down like a bride's nightie until we switch it off ourselves and then back on again. It's worse on iPlayer where it also pixellates, then freezes, then won't restart until we've been back to the main channels, then it works with no sound!
Bought from John Lewis, and we've had men round to it. Apparently there are only three bits inside a modern TV. A power board, a control board and the screen. No repairs to do, just replace and throw away.
We've had the power board replaced which made things worse.
John Lewis are coming back on Monday with a replacement - a curved screen TV at no extra cost - yippeee.
My geek neighbour tells me that power control functions on Samsung TVs are a known problem.