Why Is My iPhone Screen Black?

My iPhone screen turns black. Meanwhile, I can still hear phone calls/alarms but can’t touch anything on the screen. After repeatedly pressing the power button the screen turns normal.  This keeps happening randomly

I DON'T UNDERSTAND WHAT'S WRONG, PLEASE HELP !

FYI - Before this happened, my display would turn on/off every couple of seconds draining my battery. Is this related ??