Q: 6SPlus Restart Cycle

Hi there CSLATERDUE,

It sounds like you set your time to something manually and now your phone will not boot to the Home Screen. If it was a date on or before 1970 then take a look at this article since you will need to reach out to Apple for support:

If you changed the date to May 1970 or earlier and can’t restart your iPhone, iPad, or iPod touch

Manually changing the date to May 1970 or earlier can prevent your iOS device from turning on after a restart.

An upcoming software update will prevent this issue from affecting iOS devices. If you have this issue, contact Apple Support. 

If not then I would force your phone to restart with the Home and Sleep/Wake buttons as outlined here:

To force restart your device, press and hold both the Sleep/Wake and Home buttons for at least ten seconds, until you see the Apple logo.

From: Restart your iPhone, iPad, or iPod touch

 Let us know how that goes! Thank you for using Apple Support Communities.

Thank you for the update! I'm glad a retail store was able to sort you out. Just for my information, had a restore been done on the device before you set it up for service?

Thanks for answering back with that clarification! Take care!