UPDATE NOV 25, 2017 : Why does my LG G3 keeps restarting unless plugged into a power outlet?
UPDATE NOV 25, 2017
This works 100%. Very easy, I promise.
Download The "WakeLock Powermanager" app
Then do this:
1. Open the app
2. Press on "Partial_Wake_Lock"
3. Now you shoud see "0 1 2 3 4"...