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.