What the trigger seems to be is the mummy bag. Having my limbs and head completely snugged in and a stuck zipper makes me panic. It's not so bad until the morning, when I have to pee, the mummy bag is confining, I'm half awake, and the cheap zipper sticks. And then I bust out of the tent and trip over a guy line, and it takes a while to relax.
I'm also swapping black guy lines for neon orange/luminescents. My shins will thank me later.