Have the drive shaft center support checked
To DIY you need to lower the muffler by releasing all the muffler hangers
dont let the exhaust hang use a jack stand to support it in a lower than original spot then you'll need to remove the driveshaft heat shield and visually inspect the center support.It is in the middle of the drive shaft its round rubber bearing carrier that wears over time and sometimes just breaks!
Grab it and try to move it up and down. If it moves a bunch its bad and could be your vibs. HTH
Tech1