Why is my Android Moto X falling asleep unexpectedly?

A

AC Question

My Android (Motorola X) falls asleep unexpectedly. I have the sleep setting at 1 minute, but the just last few days it has started to go into sleep (screen turns black) even while I have been browsing just in the last few seconds! There is plenty of battery charge, so I can't understand why this is happening? Do you? What can I do? Thanks in advance!