I have both an iMac and a MacBook Air, both operating under macOS Catalina, Version 10.15.6. On neither system have I experienced what you're describing.
But if I were--I'd first want to establish that it ONLY happens with Excel or OneNote (i.e., that Word and PowerPoint all start and run without a hitch)... and that it ALWAYS happens with Excel or OneNote.
If that held true, I'd be inclined to uninstall and reinstall. And maybe I'd do that just based on the symptoms you've described so far.