What’s behind buzzing/shaking in D with brakes on?

[PAExplorerXLT]

When at a traffic light with my foot on the brake, I get this buzzing/vibration thatI can feel throughout the car. If I shift to P it goes away mostly but when it is in D with my foot on the brake I feel it a lot more. It almost sounds like part of the muffler is rattling or vibrating but I am not ruling the engine out.

 

[vroomzoomboom]

might be one of the heat shields on the exhaust rattling around possibly

 

[SoNic67]

Motor mounts are worn and engine shifts so much that touches a heat shield.
Temporary fix to extend the time when the mounts will fail completely:
Push the shifter in 'N' (don't pull towards you, just slide it with two fingers). Back to 'D' before moving (same way, just with two fingers). Transmission is designed for this.
Don't go in 'P' anymore, it wears out something inside transmission.