New Phone Screen Turning Off Unexpectedly.

May 24, 2016
I've been using's miui for many days now, an I like it very much. But one thing frustrates me very much. Many times the screen stops responding while playing games, while browsing, or while simply kept aside. And it turns off. Then the phone doesn't turn on.. I have to hold power button for around a minute then it comes back to life. Please anyone tell the solution. ? :(