Powers off fullyPowers off fully, or just the screen switches off?
battery is wasn't lowWhat was the battery level when it turned off? When you restarted, did it go through the whole bootup process, or did it just go straight to the screen you were on when it turned off?
i didn't remember when i restarted my phoneWhat about my other questions?
I'd suspect a hardware fault. It may be worth backing up your personal data, if not already done, as a safeguard against complete failure. At any rate, that can do no harm, so is not wasted effort even if the problem never recurs.Powers off fully