iphone 3gs randomly shutting off then back on

[doggunner50]

my iphone 3gs randomly shuts off, then comes right back to the silver apple sign when it turns back on automatically. it only does this when ob charger fully charged or when charge is high 90s etc. then it doesn't do it as the charge goes down the rest of the day.. ANY IDEAS???

 

[JamesMB]

my iphone 3gs randomly shuts off, then comes right back to the silver apple sign when it turns back on automatically. it only does this when ob charger fully charged or when charge is high 90s etc. then it doesn't do it as the charge goes down the rest of the day.. ANY IDEAS???

Since you don't say what you have tried...And I can't really understand if it is on the charger when it does this...
1) Replace the usb/dock cable and or charger
2) Hard Reset
3) Restore As New
4) Take it to Apple
5) Buy a new one