I have a 8 month old pit bull that has spasms while she sleeps. They get pretty severe, where her whole body is shaking and she is whining. It starts in her paws and legs, then her hips/shoulders and face/lips. They last maybe a minute, but she will have them once or twice while she is napping. They wake her up sometimes, but most of the time she sleeps straight through it. It doesn't seem like she stops breathing so I don't think its apnea. We rescued her off the streets, so we have no idea what sort of life she had, if she was abused or not.
I also agree. It does sound like normal dreaming to me. If you have any concerns, a vet visit is always your best recourse, as we on a forum, can't see your pet, nor can we distinguish between your pet's "normal" behavior.
I have always assumed that Max was having a bad dream when he does that. It happens a lot when he's napping and I usually wake him up. In my mind, he looks relieved to see me and glad to be awake. Who knows what really goes on in their heads? But I am pretty sure Max was abused before they rescued him at the shelter based on the way he cringes if you reach for him wrong. I have had him 7 1/2 years now. So if he's dreaming about those first two years of his life, it can't be a happy dream.