If you have been using your system heavily, with multiple workspaces, various applications that are not entirely memory efficient, these combined factors can lead to your interface feeling sluggish.
In order to resolve this issue without having to restart the entire system issue this command in a terminal windows to restart mind and preserve your workspaces and windows.
pkill -HUP -f "cinnamon --replace"
References:
https://askubuntu.com/questions/143838/how-do-i-restart-cinnamon-from-the-tty