This seems to happen maybe once every 3 to 6 months. It's a couple years old Motorola Moto E. I take the phone out of my pocket, press the button on the side to wake it up, and then see the screen is so dim I can't read anything. Happened yesterday. Had to wait until I got home, go into a dark room so I could barely see the display and press the Settings button, Display button, Brightness level, then move the slider that was all the way to the left, back to the right. Lucky I didn't actually have to use the phone before getting home. I know it worked fine a half hour before because I made a call. I don't think the brightness setting would have changed by itself just from being in my pocket. Any ideas?