Why do dead snake move

I’ve actually experienced this.

I killed a huge Timber Rattler which was threatening our cat. Knowing that rattlesnake meat is regarded as a delicacy, I decided to fry it up!

I cut off the head, then skinned and gutted the snake. Very much like cleaning a fish.

As I final step, I washed out the cavity under a stream of cold water.

And that was enough to fire the nervous system of the snake, which suddenly and violently writhed in my hands. Scared the daylights out of me! I threw the carcass into the freezer, slamming the door shut behind me.

The video at this web site shows (with a fish) how this happens: