Chosen Solution
I was given an iPhone 6sPlus, The phone restarts at random. It took several tryes to finally get through setting the phone up, just getting through the set up. I just want to use the phone to try different things with that I would not do with my personal phone. Every once in a while white lines go across the top of the phone and the touch does not work. Could this be a part of the reason it would restart at random?
Grey / white Horizontal lines at the top with no touch indicate a touch IC fault. Will require a reputable repair shop that does micro-soldering for iPhones to fix. Restarting on the other hand can be a worn out / bad battery.
