If you've ever wondered why dogs turn around several times before flopping down on the floor, the answer is simple genetics. They've been genetically programmed to trample their sleeping areas in the wild so that the grass is tamped down to make a comfortable resting place.
Although your dog have the finest dog bed money can buy, he still feels the urge to circle before lying down, even in the comfort of the modern home. It's nature at work. Nature is the reason dogs gobble their food. The most successful survivors were able to eat fast before other members of the pack could grab a share. Wild dog cousins didn't know when his next meal would come, so being the fastest gorger was a real advantage.
Source - www.thepetplace.com