I agree with ginger that he's probably dreaming and acting out chasing a squirrell or something. One thing that help is regular daily exercise. Most dogs don't get near enough exercise and that's when problems get started. At 8 months, your dog is old enough for daily walks and still needs some play time like chasing a ball with you. Puppies need energy bursts throughout the day with periods of rest and sleep in between. If they burn off enough energy they sleep better at night - just like we do! :-)
Are you absolutely sure the jumping in his sleep isn't dreaming? Some dogs are very physical in dreams, they paddle, twitch, their legs go nine to the dozen, they sometimes jump, howl, whine, etc....all in their dreams!
I am not saying it IS that, of course, just checking....
Throwing up a couple of times in a week, as a one-off event isn't too worrying, especially if the cause could be he'd eaten something he shouldn't, but with a very young pup, dehydration can be a threat. So I'd say if he throws up any more -get him checked out...and you could mention the sleep-jumping to the vet too, see what they say.