Randomly happening issue is faced by many iPhone X, iPhone 8 users with latest release of iOS 11.2. A black screen comes up with a circle spinning randomly.
After updating to iOS 11.2, it happened black screen loading circle when swipe up and down frequently at the bottom of phone, also Hitting the camera button seems to trigger it as well. Below is the video that one user captured while the issue is happening.
Lots of users have been reporting iPhone X/8 Plus black screen with loading circle. Their iPhone appears to be dead and won’t turn on. You should try to hard reset your iPhone to check if that helps.
Apparently it’s an Apple Bug, for the meantime; disable ALL your notifications from the settings. Do it for every single application. This may prevent black screen issue on iPhone X/8.
Fix 2: Use Siri option
While the iPhone is stuck with spinning wheel on black screen try to simply ask Siri to turn off Wi-Fi and turn it back on. For some users this has helped to get rid of black screen on iPhone.
For those who is looking for temporary fix like myself, you can go to Settings > General > Date & Time, set your date manually to a date before 1 Dec (Eg. 1 Nov). It will fix the black screen issue but some of the apps like WhatsApp cannot use anymore as date is incorrect.
If none of above helped, Try to set the phone back to factory settings and test it again, without using any backup data.
If it still does that, get it checked by Apple or an Authorized Apple Service