Coco does it too which has resulted in a bitten belly when she came up against an aggressive dog. She does it with people too - she sort of curls around then goes down on one shoulder so that she is belly up.
Totally submissive behaviour by Coco and probably from yours too.
Yep Poppy does it too. I think she's just showing she's not a threat - she's done it to horses and Shi Tzus! She's now 14 months and is definitely doing it a lot less, but there are a few bossy dogs we meet that she always does it to.