You're speaking with Dr. Michael Salkin. Welcome to JustAnswer. I'm currently typing up my reply.
Ella, I'm sorry that your question wasn't answered in a timely manner. The main differentials for Scrappy's behavior are normal (if exaggerated) REM sleep; and waking from a complex partial seizure (also called psychomotor seizure) which is defined as focal or asymmetric sensory or motor activity involving any part of the body and which may be associated with autonomic signs (salivation, vomiting, diarrhea,"licking his chops"/nausea/acid reflux) and is associated with a change in mentation (mental status) and/or behavioral abnormalities. When seizures first rise between the age of 1-5 years, idiopathic (unknown cause) epilepsy is most often diagnosed.
Scrappy doesn't need to see a vet unless he truly is seizing and another seizure arises within 24 hours. This would be called clustering and can presage status epilepticus - the state in which seizure activity doesn't stop and would require a vet to heavily sedate or anesthetize Scrappy. Mark your calendar for these eventa and for just what you witnessed. Scrappy's vet will need all the information you can gather before deciding if anticonvulsant medication should be prescribed. Most of us will accept one mild (lasting less than 5 minutes, no thrashing about, no loss of consciousness) seizure monthly before considering anticonvulsive drugs. See if you can video one of these events. This is a good example in which a picture is worth 1000 words. The video will help Scrappy's vet (and I if I can see the video too) determine which scenario I mentioned is present.
Please respond with further questions or concerns if you wish.