This article explains how to quickly restart an iPhone. Need to return your phone to the state it was in when it left the factory? Perform a factory reset instead.
Step by Step: How to Restart an iPhone | All iPhone Models
To restart an iPhone 14, iPhone 13, iPhone 12, or iPhone 11/XS/XR/X, follow these steps:
Press and hold the side button and volume down buttons at the same time. Volume up also works, but if you use it you may accidentally take a screenshot.
When the Power off slider appears, release the Side and Volume Down buttons.