A growing number of iPhone and iPad users are reporting serious reboot and respring issues.
Around the world, users are reporting that after 12:15 AM, incoming notifications from apps that use daily or repeat settings can cause their devices to suddenly use 100 percent of the CPU and then soft reset.
Apps with daily notifications (workout apps, medication reminder apps, etc), in particular, seem to be triggering the crash… but only after your device’s clock passes 12:15 AM on December 2nd, 2017.
Apple is currently recommending that affected users set their device’s date back by one day, but that may cause other problems.
The best fix appears to be disabling notifications from any apps that use the local settings(Settings > Notifications > the app in question > toggle “Allow notifications”.)
Other suggestions is to upgrade immediately to the latest 11.2. Once you’ve gotten your device to stop resetting, update iOS. Apple has just officially released iOS 11.2 to all, and it appears to fix this issue — but you’ll still need to get your device stable enough to update, first. Once you’re on 11.2, you can turn all those notifications back on.
If your iOS device isn’t crashing after December 2nd at 12:15 am local time, meanwhile, you likely don’t need to do anything. You probably don’t use any apps with local/scheduled notifications, or you’ve already got them turned off.