It was the smart TV updating on its own. Many were very upset about this and installed a true power off switch. I used to use a switch bar to really turn it off.
Try Samsung's latest firmware and if you don't use SmartHub, disable that.
I have a Samsung un46f8000 TV that occasionaly comes partially on. What I mean by that, the Samsung logo light comes on, the red light (I'm assuming "standby") light goes off. It swtays in this state for a minute or two then shuts down. Neither the picture or sound come on. What causes this and is there a remedy?

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