https://www.404media.co/police-freak-out-at-iphones-mysteriously-rebooting-themselves-locking-cops-out

Apple has quietly introduced a new security feature with the release of iOS 18.1. This feature, designed to enhance data privacy, automatically reboots iPhones after periods of inactivity.

The purpose of this “inactivity reboot” is to transition the device from an After First Unlock (AFU) state to a Before First Unlock (BFU) state. In the BFU state, encryption keys are not stored in memory, making it significantly more difficult for unauthorized individuals, including law enforcement, to access the device’s data.

This security measure aligns with Apple’s long-standing commitment to protecting user privacy. By automatically wiping encryption keys from memory, Apple effectively raises the bar for adversaries seeking to compromise iPhone data.