Hello Dr. K! I'm Gunasekar and I'd be happy to help you with your question.
I understand that you are experiencing issues when running the Office applications on your Windows Operating system. This particular error "Updating Microsoft 365 and Office, please wait a moment " (or) "Unable to start" message appears when the updates for Office applications are interrupted.
In this situation, you could try repairing the Office applications from the app settings and check if it helps.
A. Click Start and select Settings.
B. Click Apps and Features.
C. Find Microsoft Office 365 in the lists, and click three dots next to it.
D. select Modify.
E. Perform an Online repair.

When it is done, restart your PC and open the Office applications again.
Related article for your reference:
https://support.microsoft.com/help/7821d4b6-7c1d-4205-aa0e-a6b40c5bb88b
I hope this information helps. If you have any questions, please let me know and I will be happy to help you further.
Best regards,
Gunasekar N