Hello Jason1609,
Thank you for using Apple Support Communities. Based on your post, the Mail app shows blank white pages where content should show up. We'll do our best to assist.
Does this only happen when you receive the incoming notification or when you open up the Mail app to view these emails?
Have you tried to remove the Mail app from the Dock? If not, let's try that first: Use the Dock on your Apple Watch
Under section, 'How to remove an app from the Apple Watch Dock'.
Then restart the Apple Watch normally: How to restart your Apple Watch
After removing the app from the Dock and restarting it, test it out a bit.
Should it continue to occur, does it seem specific to an email account? Do you have any of these issues on the paired iPhone?
Wishing you well, take care.