Galaxy J7 in a restart loop

For several hours today, my phone has been waking up every 45 seconds, showing the initial swipe screen, and then returning to black.  If I am quick enough to swipe it, I get to the security screen, but after I draw my security code it goes black again.  I cannot keep the phone awake long enough to turn it off.  It is plugged in, still looping, and has been at 82% for two hours now.  If I call it, it does not ring. Holding the power button does nothing.