So I have an iPhone 6S running iOS 9.3.2 and recently, I have observed this very annoying trend.
The phone switches off automatically when the battery level is around 15-25% [It always happens in this range].
I might not be using a very power consuming app, maybe writing a mail or checking my messages and it turns off. When I switch on the phone again, it automatically turns off within a minute.
Only when I leave it as it is for 15 minutes maybe, it turns on again. This is not regular but does happen once every 4-5 days.
Is there anything I can do to investigate and maybe get rid of this issue?