My dog does this too. I did some research and I didn't come across anything that indicates HD, but I did find that it can be due to abdominal pain. My dog was really sick a couple months ago and had every test I can think of and xrays. Nothing came up, so I have concluded that she is just a stretcher. I will continue to watch her to make sure that I don't see signs of discomfort, but she has been doing this forever.
Misty- Samoyed Mix, Tannor- Golden Retriever CGC
Robyn- GSD CGC, TC, Midnite-GSD CGC,TC, Brennan-Golden Retriever CGC, Batman-Husky/Greyhound , Apollo-GSD