After charging my iPhone 12pro and I ask Siri a question, there is no audio response but just the time or weather on the screen. To get the Siri audio to work I must restart my phone. Any clue as to what is going on?

Set up "Hey Siri" to help Siri recognize your voice

Go to Settings. Tap Siri & Search. Turn off Listen for "Hey Siri," then turn it back on.

If "Hey Siri" isn't working on your iPhone or iPad - Apple Support

If you have a hearing or sound issue on your device then please try some of these processes to set it right

1. If you have a distorted sound issue on your iPhone --> If you hear no sound or distorted sound from your iPhone, iPad
2. If you are not able to hear the other person, click this...>If you can't hear a person on a call or voicemail or if the sound isn't ...
3. If you only hear through speakerphone mode --> If your iPhone is stuck in headphone mode - Apple Support
4. If the other person is not able to listen to you then please click this to identify the issue --> If the microphones on your iPhone, iPad, and iPod touch aren't ...

If the above options do not mitigate the issues then Contact your carrier and then Contact Apple Support