Why does my dog keep trembling even when lying still?

Constant trembling may be a distemper aftereffect; distemper attacks the nerves, and involuntary trembling likely is nerve damage that is often incurable, so care for the dog’s diet and life closely.

Also check if the environment is too cold causing shivering, especially for short-haired dogs; keep it warm. Dogs also twitch in their sleep from dreams. Finally, many painful diseases cause trembling, such as acute abdomen, pancreatitis, and disc disease; take the dog to a hospital to find the cause.