A cone around your yorkie's head! lol j/kidding!
I like the boots idea.
Could it be just boredom? Like when a dog chases his tail? I have also thought this when Casper looks like he is play fighting with his feet. Eg, a sign of a dog chasing his tail is that he is not totally fulfilled- whether I believe it or not it a different matter!
Good luck anyway and I will let you know if I find any methods that work-
Another method on here recently when a similar post was mentioned- a lot of people suggested changing your kitchen floor cleaning product-
Vix xxx