The first night we got Darwin I was so worried and scared because he started shaking in his sleep and making a whining wheeze like noise. I woke him up, and I was paranoid he had had a seizure or something. He was completely fine, though. He still does this. He will fall asleep and then every once and a while his paw will start twitching, followed by his entire body twitching. This is always accompanied by whining sounds. Is this just a funny dog quirk, or something serious?