Also which model phone do you have?? Guess I should have asked that. If it's not a 7 or 7 plus, I think you will want to hold the home button and power button until the apple logo appears. Sorry for mixup if any. I did fail to ask what phone you have. Olde iPhones use the power and home button. And again, sorry for any confusion if any.
Okay, holding down the power button and the home button got it to reboot, finally! iTunes connected and seems to be sinking, but it STILL on step 2 of 6. Usually it backs up faster than this. I downloaded a grocery store app this morning. Could that be what is wrong? The phone continued to work all day after I downloaded the app, though.
Oh, iTunes just finished backing up. Have any idea what caused the phone to go dead?