This is one of her favorite napping positions. No I don't know why.

Can relate. Under the covers - too hot. Out of the covers - too cold. Under the covers with one leg/ half my trunk out - juust right.

Laying and sleeping in really tight contact with the siblings is how dogs grow up. Human babies love the feeling of being "bundled" up, too (don't know the appropriate term here at English is not my mother tongue.)

Maybe the dog is simulating that?