How old is your puppy? Shivering is a sign of hypoglycemia (low blood sugar). Toy breed puppies, especially those under twelve weeks old, are prone to it. Here are the signs in order of severity:
Classic signs of hypoglycemia
lethargy (lack of energy)
weakness
head tilting
"drunkedness" - wobbling when walking, unbalanced
hunger
restlessness
shivering
ataxia - usually lack of muscular coordination, but maybe changes in head and neck movements
disorientation
stupor
convulsions or seizures
coma
Your puppy needs frequent meals, about 4-5 times a day. It's also a good idea to have some Nutrical on hand.
Here is more information about hypoglycemia:
http://www.angel-litemaltese.com/Hyp...se_puppies.htm