Phone Not Turning On

My iphone 7 turned off and will not turn back on. It is lighting up with the apple logo and then going blank repeatedly. It isn't actually powering on. I tried restarting it using the side lock button and the down volume button because the home button stopped working last week. It gave me an "unknown error" when I tried updating and restoring from computer and yes I tried charging it. I can't afford a new phone right now as I am a student. I don't know how to fix. Any suggestions?