Why does my dog get jittery when I pet her ?

She is probably just really happy to see you. And you should always take a dog outside to potty immediately when you wake up or come home. They almost always have to go, and excitement makes it even harder to hold it. Once you are awake, she is probably anticipating that now she gets to go outside for potty and if it doesnt happen right away, she leaks. I wouldnt worry, I do think its nothing more than she is very happy to see you and hear your voice. Especially since she does calm down after a few minutes. :)