If your TV has turned itself off a single time this could be due to a sleep timer. A sleep timer can be set so that how to restart app on samsung TV will switch itself off automatically after a certain amount of time. If your TV switches itself off you should check to see if a sleep timer has been activated.
Unplug the TV from the outlet for 30 seconds, and when plugging it back in, plug it directly into an outlet that you know works properly. This is called a 'soft reset' and should recalibrate the TV.