My kitten did something very similar last week and was shivering a bit. It was a saturday so i kept an eye on her, ready to take her to the emergency vet as soon as needed, but there was no other change in her behaviour (eating - playing - using the litter) and it only lasted a coulple of hours (I panicked immediately though...).
She's fine now. I would still advise you to phone your vet asap and ask for advice.