Hi, I found this thread after googling the symptoms my cat is having. I watched your video and his spasms are exactly the same as my cats. They even look like they are the same breed! My cat is not having any other trouble. He is slightly overweight, 3yr old neutered male. Did you ever find out what caused these spasms? My cat doesn't seem to be in pain or anything but every time he lays down his body seizes up like yours in the video. Thanks!