"A new job, promotion at work, college course, a new challenging hobby, working two jobs etc
Those are literally the only times I get symptoms."
To me this is absolute proof that there is emotional stuff at work here. However, that said, perhaps you need to step back from the emotional work. I think there is a point, which Sarno makes in his suggestions of "getting back to life" that we need to incorporate the work into our daily life, belief, and the way we operate taking into consideration the personality traits he outlines.
What does "boredom" entail for you? You mention only things like a "Challenging" new hobby and work or study. None of these things truly sound fun. They sound like pressure. Can you mix things up with "Fun" stuff - it's OK that the fun is mindless or relaxing (as much as it can be right now) or have no meaning. No accomplishment, no striving, no bettering yourself, no learning something new as in knowledge. In essence, life is a balance. Check your balance. Maybe even write a list of stuff that is triggering vs. stuff that is "boring".
Does your mind always want to do the stuff that is "Unsafe" - triggering. Like a drive to do these things. Some TMS writers/personalities (whatever you want to call them) find there is an addictive quality to a nervous system in hyperdrive. Since the mind naturally wants to be a little more negative it can be a challenge to enjoy the quiet moments. You might actually find you really hate those quiet times. What is attached to the boredom? How do you feel about yourself in those moments? I know my mind LOVES to be busy and feel like it's always accomplishing ANYTHING. It has strong emotional attachments to the fact that I was never taught or shown that love is unconditional. There were always conditions and I was trained that showing love in return meant "doing" (to please someone else). Although I can meditate, sitting and reading a book at home is difficult. When I go on vacation or am away from home, I can read for hours! But at home I must "accomplish".
Perhaps this kind of mind churning is similar for you.
What do I do about it?
NOTHING. I don't worry about it. I get symptoms and I don't worry about them. They are a pain in the as* but I'm not trying to avoid or fix them. Sure, like you I absolutely notice what the triggers are (which I think is a fantastic observation on your part) - but I also try to recognize that there is an emotional component and a mindset that is driving them. What is the work? Compassion. Simply recognizing that it's it's there and not trying to fix it or force it. I don't really dig at the emotional stuff because I already know what it is and I know that over time this stuff softens when you simply recognize it's there.
I am also very aware of the things I might think are absolutes like thinking there might absolutely be no emotional stuff behind things - for myself, that's simply a sign of resistance. Softening the black and white thinking around it and opening to the possibility that there might (
@Rabscuttle has written quite a bit about this softening towards old belief patterns) has really made change.