I upgraded my old iPhone to an iPhone 4 via O2 just before Christmas. No problems until about a week ago when it would suddenly shut down, and then reboot itself. This happens throughout the day, not just once a day. This has continued to happen. It also won't charge as it continually shuts down and then reboots.

During one episode, the whole screen went a fuzzy green colour and continually buzzed for about five minutes.

I've restored the phone back to factory settings twice and removed all apps but, still to no avail.

Anybody had/have this problem or know of anyone who has, and if so, what did they do to rectify it?

Any help/info would be greatly appreciated :-)