Thank you for your question. Although without being able to examine you I can not offer you the specific advice on diagnosis and treatment that you need, but I would try to provide you some relevant information about your health concern.
Your symptoms could be suggestive of either some nerve injury or a pressure on the nerve due to the muscle spasms after that surgery. Another possibility in your case could be damaged the soft-tissues such as muscles and ligaments. Since you have persistent shaking of legs, I would recommend you to see a neurologist who can evaluate the details of your case and could better determine the insight of your situation. In addition, it will be best if you would also visit a physiotherapist to let him/her assess your health concern as well. Hope this helps.
Well, it could indeed be that the spinal nerves are flaring up and causing this. The spine settles down after an operation, and could be some nerves are now newly irritated. I have problems with my legs from a back injury, and I take medicines for it, but sometimes they'll bother me anyway, my legs will kind of seize up, and sometimes I even feel it in my upper body, which other people who have restless legs syndrome will get that. The driving a car thing is quite common for RLS people, which can be triggered by back problems.
But what could be happening to you is, you might have a little problem with vitamin/mineral deficiency or not enough protein in the body, either of which can make you feel kind of weak and shaky. If you do not think that is the situation, then the last thing that comes to mind is anemia, which your regular doc can draw blood and look specifically for that, as well as look at your other vit/min levels too. Anemia will sometimes make you weak and shaky.