Help! Answered

Stupid question: You did not connect any new device recently to the TV using a HDMI cable?
Most TV's offer CEC and other functions that allow a connected device to turn the TV on and off for example.
If in doubt disconnect all but the earial from the TV and then add one device at a time to observe what the TV does.
I'm quite confident your culprit is not the TV but something plugged into it.
External HDD maybey for recording your TV shows?...

It would be funny if someone were pranking you with the old TV-B-Gone.

https://en.wikipedia.org/wiki/TV-B-Gone

but I think that possibility is remote, if you will forgive the pun.

Also you did not mention the amount of time, between these turn on, and turn off, events.

I think the TV-B-Gone has a period lasting a few minutes, corresponding to the amount of time it takes to cycle through all of its codes.

AussieAlf's hypothesis, regarding power quality, seems more likely to me.

https://en.wikipedia.org/wiki/Electric_power_quali...

Although I am not quite sure how to reconcile this power quality hypothesis with your statement, "Nothing else is doing anything. All lights, fan, xbox, etc work."

I mean, I am guessing that a light plugged into the same circuit, and turned on, would flicker when the power to that circuit was flickering.

If you disconnect all devices from the TV, including aerial and just leave it powered, does it still power off? Did you have a storm or other turbulence since the TV last worked OK? Has it being giving problems recently or just suddenly startd powering on/off after being fine before?

Hey 19carebear81,
I had a similar experience just a few weeks ago, where my coffee machine was doing the same. I plugged in a light and it worked fine for a while then it started flickering on and off. Turned out to be a fault with the switch which was arcing internally.