, you should first try a , which does not delete your data. If the device remains unresponsive, you may need to use Recovery Mode to restore it to factory settings, which will erase all data . 1. Force Restart (No Data Loss)
Use this if the phone won't boot past the Apple logo or is disabled by a passcode. Hard reset iphone 4 Dead Iphone 4 Hard Reset
This method is used when the phone is frozen or has a black screen but is otherwise functional. , you should first try a , which does not delete your data