Dog Sliding on Floor, Help!

I have a 2yr. old male neutered Pomeranian/chihuahua and as of lately he has been sliding his body across the floor. He uses his front paws to drag himself across the carpet. Is this normal behavior? He doesn't have fleas or anything and he does this at different times.

Does he do it all the time? Or just from time to time?
   
Has he been groomed lately? Maybe he has an itch, & needs the dead fur cleared out.
   
What kind of carpet: low pile or high pile? Hard or soft weave? The low-pile hard-weave kinds make great scratching areas for itchy spots. He may just like the way it feels. Dogs love a good scratch.

It's possible he has worms. Check his stool next time for them and maybe visit vet if behavior keeps up.