If your TV is automatically turning off at fixed intervals, this could be due to certain TV settings that have been enabled. To turn these settings off, simply follow the steps below:
Press the remote control's Menu button, select "Sleep timer" and set it to Off.
Navigate to the TV "Settings" on the top right of the home page.
Navigate to "Devices Preferences."
Select "Power".
Select "Auto Standby" and toggle it off.
Go back to "Device Preferences" and select "Screen saver".
Select "Put device to sleep" and set it to "Never".