PS4 turns itself off.

So, question is basically in the title.
I have been dealing with this issue for about a week now. It only occured 3 times, but I want prevent anything bad before it is too late. If it isn't already the case. What basically happened is that I was playing Mass Effect Andromeda and then left the PS4 for about half an hour. I left it turned on as I wanted to continue to play. After I came back and grabbed the controller and wanted to turn it(controller/joystick) on, then the PS4 turned itself off. Then after I turned it on it showed me the "PS4 was shut down improperly" message.