How to skipt the prompt for time-triggered automation Shortcuts in iOS13?
There is a workaround that I have gotten to work in my testing, but if you use automatic do not disturb you might have to set it to only run at the specific time that DND is enabled automatically.

Basically set auto DND and then make an automation for when DND is turned on. In order to ensure that it won't run whenever I use DND, I created a few shortcuts.

MatchTime
and DND Auto

Just set a DND enabled automation to run the "DND Auto" shortcut