IMO, this is a neurotic behavior. These are often the toughest to get rid of. It will likely take a lot of dedication to get this done. The first thing I would suggest is lots of exercise. Dogs must drain their energy or it will come out in neurotic ways like this. I would also suggest trying to socialize your dog well if it is not already. Those would be 2 helpful step however might not completely solve it. I really think this will take a long term plan. I would read up on dog psychology.