Impossible to say without more information.
Do a factory reset and don't reinstall any apps. If it still does it, you've a hardware fault of some sort (will take more to diagnose what), so if you have any warranty or return you should send it back. Otherwise install your apps gradually, a few a day, and see whether it starts again.
I know that's tedious, but being systematic is the only way to really identify the source of the problem.