What is his breed and age?
Is he scratching like he is trying to settle down and cannot (i.e. scratching like he is rearranging the bedding)?
Is he scratching like he is digging a hole?
Are there any other behaviors happening at the same time - i.e. is he panting? acting anxious? acting like he's distressed or in pain?
What do you mean by continually? How long does he do it for? What gets him to take a break in the behavior or stop?
Is he on any medication? Does he have any health problems that you know of?
Does it matter if you are there or not?
Does he do it more during a particular time of the day or night?
Does he do it more during times of noise, times of quiet, storms or weather changes?
Thanks for answering these questions. I'll get back to you once I receive the answers.
I'm thinking that your dog's behavior is anxiety-based behavior, basically an obsessive compulsive disorder (OCD). I'm thinking this because your dog's behavior requires no or few stimuli to trigger it and he digs in a focused, invariant pattern - i.e. it goes on all night. Furthermore, it seems to be an OCD because it does not respond to "quick" managment. When you try to manage it by holding him, as soon as you let go, he starts again. Also, anxiety in the form of storms has triggered this behavior in the past - however, it lasted for a shorter time period.
That said, I'm not sure if something external or internal triggered this OCD behavior. An external trigger would mean that something could have scared him at night around 4 days ago (can you recall anything happening? or anything that changed in his environment?). I had a 6-year-old golden retriever who all of a sudden became scared of ceiling fans when they were set on low. I can only guess that maybe she was lying under the fan and something fell on her and the first thing she saw was the fan. But I'll never know for sure. Likewise, you may never know for sure.
Internal triggers would be related to your dog's health. Old dogs can suffer hearing loss, arthritis, cognitive disfunction, and other health issues that can increase their base level of anxiety. The first thing that I would recommend is to have your veterinarian give your dog a complete geriatric check-up. If nothing pans out that decreases your dog's compulsive digging behavior, then I would recommend contacting the behaviorists at U. of Penn. Following is their contact info: (The behavior service at Ryan Veterinary Hospital at the University of Pennsylvania School of Veterinary Medicine can help if you encounter serious problems in training your dog. Please leave us a message at(NNN) NNN-NNNNor e-mail email@example.com.)
Hope this information will help Winston.