When using Apple podcast on my phone is there a way when one podcast ends, the next one starts automatically?

In the Apple Podcasts app on iOS you can accomplish this by tapping the three dots in the upper righthand corner of your library and select "New Station" from here you can select the shows you would like to play back-to-back and configure the options to suit your needs. After creating your station it will appear in your library automatically.

For further reference see: Organize your podcast library on iPhone or Create and manage a station in Podcasts on Mac - Apple Support

Hello, here is an example I created that might help you. In this case, podcast "A" is 2.5 hours and podcast "B" is about 1 hour.

• configure the station to play the most recent episode or the most recent n episodes (you can also group by show)

• When you play your station tap the episode at the very top to play the station. If you go to the controls as shown in the image below you should see "Playing Next" under the "Episode Notes." The next episode will automatically play after the first assuming you do not select a show outside of the station or start the show in your station from outside of the station.