Why is my dog shaking?

I have an almost 5 month old husky/gsd mix pup, and just recently (about half an hour ago) she started sitting BEHIND the couch (note, she never does this, she's always right at our feet or trying to sit with us) and when I looked behind there she was shaking. Not in a scared way, more of a shivering way. She's now sitting on the couch beside me and she's still shaking, and it's really scaring me. What's going on?