iPhone talks when plugged in to charge

Make sure that you don't have a Shortcut set to speak the action when you connect your phone to the charger.

Here's a third-party video describing how you would create one, so it should help you look to see whether one exists:

How To Change iPhone Charging Sound - Siri Speak Fun

Does it talk at other times? That’s a feature of VoiceOver.

Glad I could help!