Facetime popups

I just took my phone of the charger and when I turned it on Sign in to Facetime - enter your Apple ID Password. Well, I did and when I pressed OK, the same Sign in to Facetime popped up. No matter how many times I try it won't except my password and won't let me get into my phone at all. What could have happened? I feel like I'm being held captive by this Facetime Pop Up.