here is how to fix your iPhone by yourself and
stop the random crashing
Try to update your device to iOS 11.2. After you tap Download and Install, the download will continue even if your device restarts. Wait for the update to complete.
If you can’t update, turn off notifications for all the
apps on your device, then update your device to iOS 11.2:
1. Tap on Settings >>> Notifications. 2. Tap an app, then turn off Allow Notifications. Repeat this step for each app. 3. Update your device to iOS 11.2. 4. After updating, tap Settings >>> Notifications and turn Allow Notifications on again for each app. If you’re unable to update or still have issues after performing the update, contact Apple Support.
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