Something happens to my cat, it starts with his tail going crooked?

My adult male cat has recently starting to have these "episodes" his tail will get crooked and his pupils big and he will lie down and his limbs will either stretch out or curl up.. the whole time he will pur. He is up to date on his shots and no other issues. I have to wait for our vet to return from vacation, and I cant seem to find what this could be on my own, any help?