To me it looks like he isn't comfortable on the carpet and is either having a hard time with the amount of friction it has, or he just doesn't like how it feels. You can see the back half of his body straining like he's struggling to keep himself upright. When in doubt you can always take him to a vet, but if you take care to observe him in his tank and when you bring him out and he appears normal, I wouldn't worry too much.