My iPhone stop working
My phone started turning off and on now it’s just staying on the apple logo
iPhone 6s Plus
Frozen phone or Logo Bootloop or Stuck on apple logo
see the process below, using the Update option if possible.
Work all through it. There are several stages.
If your iPhone, iPad, or iPod touch won't turn on or is frozen - Apple Support
There is no guarantee you can save any data since your last backup if you need to use the Restore option.