How to stop iPhone from automatically playing when it connects to my car stereo.

If there is a setting to stop autoplay it would be on the stereo. In most cases the stereo will automatically start playing when the source of the music is set to Bluetooth. Here is a possible option that will create a shortcut that stops the music from playing when connected to Bluetooth. The downfall to this approach is that to get music playing again through your car, you will need to start playing it on your phone.

• Open Shortcuts app
• Tap Automation at the bottom of the screen
• Tap "Create Personal Automation"
• Tap "Bluetooth"
• Tap "Choose" under Device and select your car
• Tap "Done"
• Tap "Next"
• Tap "Add Action"
• Tap "Media"
• Scroll down to the Playback section and tap "Play/Pause"
• Tap "Play/Pause" on the top of this screen and choose "Pause"
• Tap "Next"
• Tap "Done"

If you decide you don't want this automation after creating it, you can simply delete it from the Shortcuts app.

More than likely that is the problem. iOS 17 added an additional step that can ask you if you want to run the shortcut when triggered. The info in the User Guide says this:

Some personal automations can run without asking you for confirmation when they’re triggered.

1. In the Shortcuts app  on your iOS or iPadOS device, tap Automation .
2. Tap the automation you want to run automatically.
3. Turn off Ask Before Running, then tap Don’t Ask to confirm your choice.
4. Tap Done.
5. The automation will not notify you when it’s triggered.

I just tried the steps again and it worked, so was there any steps in the instructions that didn't match up when you tried? After you choose your car, tapped Done, then tapped Next, did you have the option to Add Action? Also make sure on the second step you tap the Automation tab on the bottom of the screen, then tap Create Personal Automation.

You can delete the automation you just created and try again.

Yet another annoying and useless "feature" in IOS 17. Similar to the posters in Contacts. There should be a way to turn off autoplay in the music app. Perhaps just remove the app. Just fire the clown who decided this was a good idea and restore the app from Ios 16.

It should be automatic. After you tap Create Personal Automation, you select Bluetooth, then your car and that is the action that should trigger the rest of the shortcut.