Why does my TV turns off after a few seconds? But the screen turns off first and like after 8 seconds the volume turns off?

Time for a new TV. The same thing was happening to ours. A good hard wack to the side usually turned it back on, and for a while there it would work for an hour or so before it shut down again. Then, as time went by, it would shut off every few seconds, even after the wack.

We looked into getting it repaired, but the cost to repair was more then a new TV.