Chosen Solution
The phone kept rebooting, then I noticed that the screen was lifting but kept trying to use and hence recharge the phone. Then realised that the cause of the screen lifting was due to the battery having swollen. I have replaced the battery but the phone won’t boot. I have tried a hard reset but it doesn’t get past the Apple logo icon.
I have you tried to restore the phone? You will lose all of your data unless you backed it up.you could try hooking it up to iTunes and putting it into dfu mode and update it first if not you might to restore it. It could also be a hardware issue try disconnecting items from the motherboard one ar a time and see if that has any effect. Make sure you disconnect the battery before you disconnect or connect anything on the motherboard.
