She does not look to be in any type of distress from that video to me at all. sleeping rather peacefully in my opinion. I am not seeing any "shivering" movements, she looks to me to be sleeping comfortably and the movements are her breathing. You have got to remember, she is pregnant and those kittens are pressing up against her ribcage so her breathing naturally will be a little labored. Not unlike we humans as well at the end of a pregnancy.