Christian Harfield, I would start with a new battery. The iPhone does some very weird things when the battery comes to its end of life cycle. Of course you should also try to put your phone into DFU mode so you can do an iTunes firmware restore. here are some great sites that will help you with it. http://www.ismashphone.com/2008/08/recov... and http://www.iclarified.com/entry/index.ph... If it comes to changing the battery the Guide is here. It is NOT easy to do but manageable, just familiarize yourself with the steps ahead of time. The battery is available right here. Good Luck and I hope this will help you out.