Macrumors keep in mind that the screen on some iPhone 14 Pro and iPhone 14 Pro Max shows horizontal lines when starting up.
The lines are green or yellow and are visible for a few seconds before disappearing.
According to Apple Support, it shouldn’t be an issue with the hardware itself, so hopefully it can be fixed in a future iOS 16 update.
Right now IOS 16.3 is in full beta testing and the final version will be released in January or February.