There have been reports from iPhone users that some of them have found their iPhones shutting down by themselves in the middle of the night, only to turn back on later. This can be identified by the alarm not going off (due to the device being turned off) or the iPhone requiring passcode unlock in the morning, which happens after a reboot.
Users can check for themselves whether their iPhone shut down or rebooted overnight by going to Settings > Battery and checking the battery usage history for the past 24 hours. If there is a gap during the night, it means that the iPhone was turned off (as shown in the example image below).
It should be noted that this issue has been reported by a group of users across multiple iPhone models and is not limited to the latest iPhone 15. However, since it doesn’t happen to everyone, it is difficult to determine the exact cause of the problem. Apple has yet to provide any information on this matter.
TLDR: iPhone users have reported instances of their devices shutting down on their own during the night and turning back on later. This can be confirmed by checking the battery usage history in the Settings. The problem affects multiple iPhone models, but the cause remains unknown. Apple has not given any updates on this issue yet. (Words: 134)