Strange Shuddering

[Alex Kowalski]

Driveshaft center support bearing?  I would drive it a while longer at a
variety of different RPMs and speeds.  See if the vibration persists and
report back.

As far as warmup is concerned, I don't do it unless I absolutely have to
(meaning subfreezing temperatures and a passenger who can't stand them.)
Put the key in, start it, and drive it gently until it's warm.  As Brett
states, it only takes a few minutes, at the most, and besides -- you're
getting where you're going even if for the first few minutes you're running
a little slow.  If your SO can't stand the cold, try kissing her.  Works for
me.  ;)