I am receiving the error:

Unexpected file found in package directory:

When I try to deploy a class that I have just created.  The file is saved in the /force-app/main/default/classes/Case_Trigger_Alert_Count.

I have also noticed that in the 'Problems' tab, I have the message:

The sourcepath ".../force-app/main/default/classes/Case_Trigger_Alert_Count" is not a valid source file path.  SourcePathInvalid [1,1]

The filename of the file I have just created and attempting to deploy is 'Case_Trigger_Alert_Count"

What am I missing to be able to deploy to my Sandbox?