Your poor dog is definitely not feeling well! It could be that she's eaten something she shouldn't and it's upset her tummy, or she could be sick.
She's hiding and shaking because she's stressed and scared, probably because she doesn't feel well. I would suggest that you seek veterinary help. Call a 24 hour emergency clinic for advice if your vets office is closed.
You can find information on dog illnesses at this url http://www.the-puppy-dog-place.com/dog-illnesses.html and information on poisonous substances etc. at http://www.the-puppy-dog-place.com/poisonous-foods.html
Best of luck, hope your dog is feeling much better soon.
