Finder resets preferences on restart
It’s possible your Finder preference file is corrupted.

Open Finder, then press ⇧ shift ⌘ cmd G. In the popup textbox, type in ~/Library/Preferences.

Locate com.apple.finder.plist and delete it. Restart your system and see if the issue persists. If it does, you can pull the file back out of the Trash and restart one more time.