Iphone 4 keeps loading after writing pin code

[Andretti]

Hello

My dad's Iphone 4 keeps loading after he writes his pin code. It doesn't freeze as he is able to write other digits while it loads.
It just keeps saying that it's opening the phone please wait and nothing happens.
We have tried to shut it down several times but it never gets past the screen with the pin code.

Does anyone know how to fix this?

 

[nikstar]

Try a reset by holding the sleep/wake button and home button down together until the apple logo reappears. Hopefully that will work.