Why is my iPhone 7 turning off and on randomly?
About every 5 mins my iphone will bring up the black screen with the loading symbol like when you turn off the phone and right after show my passcode screen.
You need to update to iOS 11.2.x
Settings > General > Update
If you can't get to update temporarily change your date to the end of November.
Then update. When the update finishes completely you can set your date back to automatic.
