I copied this from http://www.ferretcentral.org/faq/, I hope this helps.
 
        http://www.ferretcentral.org/faq/part3.html#trembling
 
"My ferret trembles a lot. Is that normal?
 
Generally, yes.  Ferrets normally tremble for two reasons.  First,
they often shiver right after waking up, in order to raise their body
temperatures.  Second, they shake or quiver when excited or frightened.
For a young kit, this could well be all the time, since everything is new
and interesting.  For older ferrets, a bath or even a good scolding could
prompt trembling.  If your ferret's trembling persists with no apparent
cause, first make sure there's no cold draft around.  (Ferrets can live
fine outdoors, with blankets and shade, but indoor lighting can cause
their winter coats not to come in until long after it's gotten cold
enough outside to need one.) If that's not the problem, check with a
vet."
 
Kris
http://groups.yahoo.com/group/CarpetSharksInk/
[Posted in FML issue 3981]