When configuring a workflow to start on a specific condition, and the start condition is "Name (previous value)" is not equal "name", the workflow does not start when the document "name" has been modified. 

This is an expected behavior due to a limitation on the Microsoft SharePoint platform. 

Conditional Start on name change is not possible due to how Microsoft updates that field as it calls a different method compared to the other fields when a change is made. 
This behavior applies to Nintex Workflow 2013 and 2016.