If you still see the support.apple.com/iphone/restore message, you can restart your iPhone in recovery mode. Below are detailed steps to troubleshoot without a computer.
Here's how to force restart in restore mode:
For iPhone 8 and newer versions: Press and hold (a few seconds) the volume up button, then release it. Quickly press and release the Volume Down button. Then press and hold the side button until you see the Apple logo.
iPhone 7 or 7 Plus: Press and hold the side (or top) button and the volume down button until you see the Apple logo.
iPhone 6/6s, SE or earlier: Press and hold the side (or top) button and the home button until the Apple logo appears.