After the end user logon Citrix DaaS session using native Citrix Workspace app, if there is no activity within the Citrix Workspace app window for the specified interval of time, Citrix Workspace app timeout Notification will be shown.
The Warning Message is "Your session is about to expire. You will be signed out soon due to inactivity".

If you do not want this notification shown, you can disable "Inactivity Timeout for Workspace App" setting in Workspace Configuration > Customize > Preferences.

Problem Cause

If Inactivity Timeout for Workspace App is configured in Workspace Configuration and the amount of idle time is about to expire, this notification will be shown.
This is expected behavior.