Hey Willem

Best thing to do here is to set that workflow up with a schedule. You can do this by going to 'cog' symbol (top right, SharePoint 2013), selecting 'Nintex Workflow 2013', 'Schedule Site Workflows'. From here you can 'Add Schedule' and select the frequency and the site workflow that you want to run.

If the workflow you currently have is a list based workflow, then recreate it as a site workflow so that you can make use of this great feature.

Note that this works in our 2010 product too, just that the menus are in slightly different places.

Interested to hear what you are emailing this group about? I'm assuming you have some sort of query running on that list and emailing the group about documents that are still in draft perhaps?

Hope this helps

Thanks so much will try it out