I'm not a vet or vet tech, but your description does sound like the beginning of epilepsy because of the head shake with the back leg movement. Here's a link:
Sometimes cat do this "thumping thing" with their back feet to shake off some litter that may be stuck in between their toes. Malia should be taken to a vet for an evaluation. If you could take a video
of her during one of her episodes to show the vet it would be helpful.
Hope a vet can give you an answer to Malia's behaviour.