It might not be submissive or stess, it might be an actual medical problem. it was medically controlled.
Pets have all the same emotions as humans, this means that with all the good may come some of the bad. One of these is anxiety which can come in many forms but is ultimately the product of fear or worry.
Dogs cannot control what their anxiety reacts to and the pet parents job is to make sure their furry friend feels safe at home. Some of the things that might lead your pet to freak out include thunderstorms, fireworks, strangers, increased company, and maybe even a new piece of artwork.