Answer

This problem only affects anyone who is running Office 365/2016 build 16.0.7668.2066, which was released into production to a small group of customers between 1/25 and 1/30.

Please refer to the troubleshooting steps provided by Microsoft to solve the problem.
https://support.office.com/en-gb/article/Windows-screen-is-flickering-or-flashing-after-logging-in-c49d12fa-f080-483c-898e-8329e46306dc