I also say that you need to know which area of the spine is affected. I have a client who has the same problem in the low back; but, also in the neck.
Decompression work is the best to start off with, then incorporate the strength. I would definitely get a doctor to clear specific exercises and/or programs to keep everyone safe.
Desensitize: The jarring thing needs to be reinforced and made a habit so the client does not make quick moves in a startling situation. You could warn the client that you will be making loud sounds without warning, which is practice to avoid panic/moving suddenly when it happens during their day.