If your LG TV turns off whenever you try to open any app, there could be several reasons for this issue.
One of the most common reasons is that the Auto Power Off feature is enabled, which turns off the TV when it thinks it isn’t being used.
To turn off Auto Power Off, press the Home or Smart button on the remote, go to Settings > General, highlight Auto Power Off, and turn the setting off.
Another reason could be that someone in your household set a sleep timer on your television, which could be the reason why your LG TV keeps shutting off. Check for existing timers set and get rid of them.
It could also be caused by a loose or faulty wall socket. Try plugging it into a different wall socket and see if that makes a difference.
If none of these solutions work, you can try clearing the cache of the app you are trying to open.
Press the Home button on the remote, choose Settings, navigate all the way down to Edit App List, and for each app, go in and clear the cache.