I found another forum that suggested the following command in Terminal, but it did not work for me (this worked for someone running Mint in VirtualBox VM which I am not). Switching the background to another image and back again also doesn't do anything.
gsettings set org.cinnamon.muffin background-transition 'none'
viewtopic.php?f=231&t=273812&p=1544926& ... d#p1544926
I'm not sure if it has anything to do with my graphics card, but I have an Intel Corporation HD Graphics 5500.
If anyone has any suggestions I'd greatly appreciate it! And let me know if you need any more information.
Thanks - Richard