Annoying Text Box/Line appears while in Notes and writing with Apple Pencil

Hello constantinos32,

To be sure we narrow this down as much as possible, is the Notes app the only app affected by this text box appearing?

In the meantime, if it's only happening with the Notes app, you can refresh it by uninstalling and reinstalling it from the App Store and unpair the Apple Pencil and pair it again to reset connections with the iPad:

1. Be sure notes are saved in iCloud or the account you use with notes (like Outlook or Google): Set up iCloud for Notes on all your devices - Apple Support
2. Remove the Notes app: Delete built-in Apple apps from your iPhone, iPad, or Apple Watch - Apple Support
3. Settings > Bluetooth > the 'i' next to the name of your Apple Pencil > Forget this Device
4. Pair the Apple Pencil by attaching it magnetically to your iPad Air then tapping the 'Pair' button that appears.
5. Reinstall the Notes app from the App Store: Redownload apps and games from Apple - Apple Support

Take care!