Why my phone keep going back to the start screen

It like when i turn my phone on it tell me to press start to continue. I press it then it send me to the screen were i have to put in my email an password. When i put my correct information in it ask me do i wanna back up my stuff up an i check it. Then when i press the right arrow to continue to the next screen it bring me alway back to my start screen if anyone knoe how to do this please help a brother out Lol.