iPhone 4 keeps turning on and off again after iOS 6.1.3 update?

[Joe]

I just updated my iPhone 4 to the latest iOS and after it finished, the phone keeps desplaying the apple logo as if its turning on and then it will disappear. This has been going on for about 20 minutes now, can anyone help?
I haven't managed to find anything on this problem specifically (although there are many similar)
And before anyone suggests, plugging it into itunes or trying to put it in DNF mode has no effect.

 

[Tasha]

Try and restart it, can't remember how too.. yourll have to google it

 

[Dany]

search on google how to enter DFU more and restore it one more time