iphone 7 plus does not turn on anymore appears black display with only apple logo

I have an Iphone 7 plus ,all of a sudden it turned off on me and now the only thing that turns on is the apple logo with a black display and turns on and off on its own .I tried forcing on off no results ,turned it off and tried to turn it back on same problem ,black display with only thing turning on is the "apple" logo .Need help