Why does my phone keep shutting down?

Okay so my Iphone 4 (ios7.1.2) is constantly turning on and off whenever it feels. I usually only am able to play on it for 30 seconds til it shuts do

Okay so my Iphone 4 (ios7.1.2) is constantly turning on and off whenever it feels. I usually only am able to play on it for 30 seconds til it shuts down automatically. If it helps, the phone is around 3-4 years old and the screen is cracked where a part of the bottom near the home screen button is has been pulled off

or:Okay so my Iphone 4 (ios7.1.2) is constantly turning on and off whenever it feels. I usually only am able to play on it for 30 seconds til it shuts down automatically. If it helps, the phone is around 3-4 years old and the screen is cracked where a part of the bottom near the home screen button is has been pulled off


or:you might need a new battrey how long have you had it

Tags:down,feel,ios7,