The problem with the wallpaper
When you turn on the phone, the time and the black screen light up, and after 1-2 seconds, the wallpaper lights up.
How to solve the problem?
iPhone 14 Pro, iOS 16
Question marked as
If you are starting from power-off it may take a second or two for a wallpaper to be loaded from storage and displayed on the screen, particularly if you have selected one of your photos as a custom wallpaper (a big file, maybe needs to be rescaled to fit the screen). I think this is probably Working As Designed and there is nothing to fix. The critical test is what happens when you continue to use your iPhone - does it work?