Hi Dima.
1. For me, stress has always been huge trigger (finals, 30 years ago, in college; birth of kids; job transitions; etc.).
2. Most folks do get hit most often at night I find that, early in a cycle, there's not much pattern; but over time the evening becomes a ritual (up at 11; 12:30; 2; 3:30;5;give up and make coffee).
3. I can't overstate how important oxygen is. I tried it multiple times over many cycles (and multiple years) before I figured out how to do it successfully. Search the forum and find the right regulator (15 lpm minimum), non-rebreather mask, and proper technique. Most docs will shy away from prescribing O2; and even when they do, the medical supply company will bring the wrong thing (small tanks; concentrarors). Bypass all that; find a local welding supply. I shied away from doing this for years; it was a mistake.
4. I hope you find a great neuro. In my experience, the best you can hope for is an empathic ear who's willing to work with you and will listen to your ideas.
Good luck with your journey.
Craig