Chosen Solution

I have a iphone6 which has just encountered a interesting issue. The phone will now constantly reboot itself. It will start up and you can enter password and enter phone but after a few minutes it will shut down and reboot again. I have had a new battery replaced about a year ago, so can’t think that would be the issue. When I have it plugged into a wall charger (apple charger) it will show a maximum of 20% and not get above that, however it will go down to about 5% instantly from unplugging from wall. Throughout this whole time (plugged in/not plugged in) it is restarting as mentioned. I cannot do anything in regards to updating software or do anything inside the settings for that matter as it will restart before completing anything meaningful. I have read that issues can arise from a mb solder or the flex cable going to the battery, but not sure how to test these. Any help or ideas would be greatly appreciated as this is really starting to bug me. Thanks in advance!

Try another battery and see how it goes, it’s not rare for replacement batteries to die around 1 year, depends on the quality of the battery.