Why does my TV turn on, flash random colors/shapes, then shut off?

Why does my TV turn on, flash random colors/shapes, then shut off?

I had forgotten to turn off my tv before I left for a few days, but when I came back it was off. Tried to turn it on and it didn't work. I reset it by unplugging it and holding the power button down for 10 seconds. It turns on now, but flashes different blocks of color and lines across the screen, then shuts off. What's wrong with my tv? Is there anything I can do to fix it?

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