How to automatically trigger a iOS Shortcut (based on location/calendar)
Unfortunately this is not possible (yet). It's a known limitation of Shortcuts in its current 2.0 implementation.

Federico Viticci mentioned this in his (epic) iOS 12 review as something he'd like to see in the future:

https://www.macstories.net/stories/ios-12-the-macstories-review/12/#content