I would try to install a fresh copy of the latest iOS, restoring your device to factory settings.
Make a full backup of your iP8+, and follow the steps provided in this support guide:
Restore your iPhone, iPad, or iPod to factory settings - Apple Support
Then set it up as new and, before restoring from your previously made backup, test it.
I you have the same issue, then you could have a hardware problem.
If your device is working fine, then restore from your backup.
If you have the same issue again, there could be some software problems (some wrong settings and/or some apps not working properly).
Regards
Giulio
Jovo
Did that work for you? My friend is having the same issues. He went to sprint and 2 apple stores already. My phones starting to do the same aswell. We both got ours sametime you did and both did the update.
No it didn’t, it actually started to get worse. I went to the Apple store and they replaced the phone. I had the new update, did a full restore through iTunes on the computer even turned off all notifications and restarted then turned everything on again. They determined it was hardware failure and just gave me a new one.
Make an appointment at the Apple Genius Bar for service. If you need to find an Apple Store - Find a Store - Apple. Also, see If your iPhone, iPad, or iPod touch unexpectedly restarts.
The problem started when I updated to 11.2
iPhone 8 Plus crashing/restarting
