Chosen Solution
Just got a ’new’ refurbished phone. Charged it fully and then did the set up thing. The phone now turns itself off to a black screen with the apple logo sometimes flashing up. Did the whole itunes reboot thing and updates (itunes has IOS 11.4) and it says yep all good to go but now as I get half way thru setup it just turns itself off then will turn back on whenever it seems to feel like it. I do the on/off and home key thing which sometimes works for a short while then back to square one. HELP PLEASE!!!
I’m guessing either the battery needs to be replaced or the small components right above the battery connector are damaged / missing when the battery got unplugged. When there is pry damage (missing or damaged components) above battery connector the phone can’t read the battery properly and you get the issue of the battery percentage being sporadic on and off charge and random rebooting. Here is guide and link on how to replace the battery, it’s strongly recommended you check for any missing or damaged components if I remember correctly there are 4 small ones right above battery connector. How to replace the battery in your iPhone 5s iPhone 5s Battery iPhone 5s/5c/SE (1st Gen) Battery Adhesive Strips
