Hi mertinbiri,
We appreciate you reaching out to us. We understand that your wallpaper switches.
We’d like to gather additional details that may help us be in a better position to assist you.
Are you experiencing this behavior on the Lock Screen wallpaper, Home Screen wallpaper, or both?
Does it help if you remove the wallpaper, then set it up again?
Also, let’s check for a software update and make sure that you are running the latest version of iOS 16.
While it isn't inherently assured that an update will resolve the issue, updating to the latest software version for your device can help isolate potential software issues.
Kindly secure a backup and update.
How to back up your iPhone, iPad, and iPod touch
Update your iPhone, iPad, or iPod touch
Take care!