whats worng with my puppie

Question
he's acting very weird and his body kind of rocks back and forth involutarily he's not playful like he usually is but if someone leaves out of a room or something he'll run after then we just noticed this the night before valintines day,whats wrong with my dog?

Answer
Hey Cheyenne. I usually don't like to take any chances with puppies.  If you think he's acting or feeling weird(especially the described rocking back & forth), I would bring him to the vet for a quick exam. Please let me know if I can help with anything else. Thanks!
-Heather