VIbration under floorboards of car at traffic light stops?

00 crown vic 145k

When i come to a stop at a light or something. I get bad vibration under the floorboards, almost like its a cycling sound exactly on time and then it stops when i normally cruise. The sounds like a cell phone vibrator going off under my feet .. I am thinking its a torque converter issue but can you be specific why and what is going on within that unit.VIbration under floorboards of car at traffic light stops?
Probably the muffler and/or tailpipe rattling against the frame.
Probably a broken exhaust pipe hanger causing the exhaust pipe to rattle against the frame.VIbration under floorboards of car at traffic light stops?
or the converter/muffler heat shield,,,very common,,,VIbration under floorboards of car at traffic light stops?
Muffler and tail pipe needs to be re mounted and secured.