why does My iphone 6 keep turning off and on

If your iOS device restarts or displays the Apple logo or a spinning gear unexpectedly - Apple Support

Hi

Have you got the latest ios software 11.2 update over your wifi.

Go to apps store download Battery life it will test your battery condition.

If battery is over 2/3 years Old it will need replacing make an appointment at Apple store.

Or go to Support.apple.com for posting details Mine took 4 days use simcard in other phone if you have one.

Cheers

Brian 🇬-1F1E7;

Hi Ceondra,

Update your software to 11.2 to help fix the issue

https://support.apple.com/en-us/HT204204