Searches for Podcasts published today (and downloaded to your device) and starts playing the earliest-posted episode right away.
This shortcut takes advantage of the somewhat-buried ability for the Play Music action to filter by Media Kind and find Podcasts, as well as actually sort the episodes by release date.
Make sure to try filtering for TV, Movies, Music Videos, iTunes U, and Audiobook content as well – Find Music can find a lot more than just music.
For some reason, this method only works with the Play Music action as well – using Play Podcasts doesn’t respect the same sort order.
(I suspect this is residual from the days of Workflow, where filtering your “music” library for this way was the only method to get at podcasts – since then, the newer Podcasts actions have been added to Shortcuts)