Although iOS & iPadOS are very reliable, rebooting your iPhone or iPad might occasionally fix strange or problematic behaviours.
To turn the device back on in the past, you either had to remember which buttons to hit or go to Settings > General > Shut Down before pressing a button. But in iOS 16 & iPadOS 16, Siri has picked up a new skill: restarting iPhones & iPads. As reported in mbsdirect.com, holding the side button or Home button while speaking “Reboot” or “Restart this device” will activate Siri. (Using “Hey Siri” may have surprising outcomes, & simply saying “Restart” usually causes Music to begin playing the previous track.) Your device restarts once you tap Restart.
