Force Restart Your iPhone
Besides turning your iPhone off, your side button can also help you force restart your iPhone, although this is something you never want to be forced to do.
Force restarting your iPhone will potentially get rid of any performance issues or other bugs that you may be dealing with. With that said, you shouldn’t force restart your iPhone every time you face a small issue. Turning your iPhone off and back on should do the trick — a force restart is typically only necessary if your iPhone is frozen such that you can’t access the power off slider.
To force restart your iPhone, you need to quickly press and release the volume up button, then press and quickly release the volume down button, and finally press and hold the side button until the Apple logo appears on your screen.