Hello SJT1971,
Let's begin by restarting your iPhone 12 Pro using the steps below:
1. Press and hold either volume button and the side button until the power-off slider appears.

2. Drag the slider, then wait 30 seconds for your device to turn off. If your device is frozen or unresponsive, force restart your device.
3. To turn your device back on, press and hold the side button (on the right side of your iPhone) until you see the Apple logo.
You can also find those steps in this resource: Restart your iPhone - Apple Support Restarting can sometimes help address unexpected behaviors.
Do you use any other Apple devices, such as an iPad or iPod touch? If so, do you experience the same behavior with your other devices?
Should that behavior still persist, you'll want to reach out to Apple Support so they can look into this further: Contact - Official Apple Support
Take care.