I sometimes get that same feeling when trying to fall asleep. Just when it seems like my body is relaxed and I am going to be able to sleep, all of sudden my brain/body has a panic and I feel like I can't catch my breath and I am going to die in my sleep.
Of course after that I give myself a pep talk and rationalize that this won't happen, and I am usually able to fall asleep after that. Or I reach a point of exhaustion and my brain finally shuts off.
One of my doctors recommended I try an herb called Relora since her other Lyme patients do well on it for sleep. I just haven't been able to try it yet. I've learned trying new meds on a work night, doesn't always pan out so well
I hope you get some restful sleep soon!