We rescued an abused dog and he seems to have terrible nightmares. When this happens, it bothers me to see him in such turmoil. Many individuals, including some of our canine friends will move around and will even make noise while sleeping.
Some dogs appear to be chasing something or possibly swimming.
Your dog may be remembering past experiences. Dogs have been known to growl, whine, wag their tails or make running movements with their paws during sleep. We can only wonder and imagine what they are truly dreaming about. Some dog seem to dream more actively than others while some individuals only dream when they have been overstimulated or are overtired. Mature animals seem to experience less active dreams but dreaming does continue throughout their lives.