The "death rehearsal" thing is familiar to me. It's a withdrawing and numbing out, even as I crave more passion & excitement in life, because I feel sort of fated to "life passing me by" and succumbing to total obscurity. I may reduce myself to the bare minimum - eat as little as needed to stave off hunger, sleep a lot or very little & without regularity, mope around in PJs and don't shower, do almost nothing but fantasize and think...and in a rough period I could do that for days on end, weeks even. But the other side of sp is to be resilient, to suddenly conquer that "death" and move into action again, which can be destructive if you're impulsively grabbing at things to induce change & its associated excitement.
I don't brag about inner turmoil nor feel superior for it, but like many 4s, I may assume I have more of it. Being able to uncover others' inner experience & note similarities with my own has been a comfort; I feel less alien. But then I can feel bad for NOT conquering the turmoil they seem to have also & functioning in spite of, so I think I go back to convincing myself I have more of it :P.