The iPhone 13 is apparently plagued by a touchscreen issue which results in the screen being unresponsive at times. This is most likely a minor software issue that Apple could resolve quickly in a future update for iOS 15.
https://www.notebookcheck.net/Some-Apple-iPhone-13-users-complain-about-touchscreen-issues-iOS-15-update-could-be-the-culprit.567470.0.html