I found an interesting community thread:
https://community.nintex.com/thread/3009
What I gleaned came from Andrew Glasser:
The URL had to be something like the following:
Site URL/_layouts/15/NintexWorkflow/StartWorkflow.aspx?List={List ID}&ID=ID&WorkflowName=MyWorkflow&Source=Item URL
This works as far as it goes--but it leads me to the Start Workflow Screen for that Workflow.
I want to go farther. I don't want my user to see that screen for my workflows there is nothing I want them to set.
I want the workflow to just run--not stop at the Start Scree.
Gerard Rodriguez came up with observation that WorkflowName could be subsituted for TemplateID. I'm going to try this with links I've created for Site Workflows as well, since everytime I recompile the link is not valid since the templateid changes.