This morning I drove home from church, parked the car, shut off the ignition and opened the driver's side door.

The internal alarm (lights on/not in Park) started pinging. With the door closed, the alarm stops. If the ignition key is in the ignition and I open the door, no alarm.

Can anyone help me please?

The alarm control module may be failing or is detecting a sensor that is not working as designed. You will need to find a shop locally that can determine what actual component is responsible and then replace it.