I had a cat that did this and I was told it was because they were taken away from mom to early. They eventually stopped but it took a while. The cat in question was indeed very tiny when he was found dumped in a yard. I don't know if it would be the same for dogs.
Misty- Samoyed Mix, Tannor- Golden Retriever CGC
Robyn- GSD CGC, TC, Midnite-GSD CGC,TC, Brennan-Golden Retriever CGC, Batman-Husky/Greyhound , Apollo-GSD