Ti Ed had I believe years of disc problems before he was fused so he would probably know if this is consistent with disc issues. But this part,

"Fortunately, I only get it very rarely and often times only when sitting for long periods of time. The intensity of the pain varies but always disappears in an instant, sometimes it is slight, sometimes it is enough to startle me and stop me from working."

sounds exactly like what happened to me with my herniated disc in the early 1990s I would be at a meeting and at some point move and I went from zero to ten to zero in like a second. Like a knife in and out. And only when I had been sitting for a while. I screamed out at times and had to explain what happened.

The diagnosis was herniated disc and they gave me PT but told me rest would help also. After a few months, the episode was over.

I herniated another disc (probably the same one) in 2012 while riding and this time got instant sciatica down my butt. I was debilitated to a point where I was not sure how I was going to get off my horse. Episodes of this pain have caused me to be nauseous. Knowing what it was and that it wasn't going away after 1.5 years of daily pain, I eventually just rested it for three months (meaning stopped riding my horse) and drove up the world-wide price of Motrin for inflammation. I am now back to zero pain. I can't produce the pain now no matter what I do. The disc injury healed. I expect to re-injure it episodically the rest of my life.

I bet PT will work for you. Good luck.