Like humans have oils on their hands, dogs have glands on their paws that leave a distinct scent on their bedding, toys, etc. Pawing at their beds provides them comfort and protection, but it also lets other dogs know that this bed is theirs and it is their territory and to not mess with them. This can often happen when there are new things in their lives. Things like a new person in the house, a new animal, or any other major change that can impact the dog. Most of their scent will be washed away when the bed is routinely cleaned but, fear not, your dog will quickly reapply his essence to the bed after it's washed to reclaim the territory. You will probably see him ferociously rubbing himself all over it as soon as you put it back in it's designated location after laundry day.