Desktop Background Changes Arbitrarily
Why does Apple arbitrarily switch out my desktop background when I turn off, then turn on my computer?
MacBook Pro 13″, macOS 12.5
Question marked as
Apple does not. It's likely that your Mac is doing this because it is set to change the image when logging into your user account or waking from sleep.
Check this in System Preferences > Desktop & Screen Saver > Desktop tab.
At the foot of this panel inspect the box labelled 'Change Picture' and the regularity for which this is set to happen. If you want to retain the same image remove the tick from the box.