Get an MRI test then go to a board certified neurologist. Send all your results to different specialists and get several opinions. Dobermans are prone to wobblers. However, if it is a slipped disk- one wrong move and it's like a bullet to the spine and will paralyzed your dog. I’m going thru the same thing now... god I hope my Doberman is going to be okay. At least I know what it is and we caught it early- well early enough. Remember, limit your pet activity!
How is your Dobe doing now? I would be checking in with a neurologist. Dobes are very susceptible to wobblers syndrome and it generally initially presents as neck pain.