First, sleeping on your hands is not good for your hands or your wrists or your jaw (TMJ).

It sounds like you would benefit from taking your pulse and blood pressure before bed or when you have these episodes. You may have something triggering an increased heart rate and BP. It lead me to think about anxiety.

Proper sleep hygiene should prepare you to fall asleep within a few minutes. Settle the house with low lights, quiet sounds, finish any pre-bed routines 1/2 hour before your targeted bed time. If you have any tasks that need to be done the next day that you may be tempted to think about, write some notes of your last thoughts and reminders. Writing things down allows the mind to let go better. Then, spend that 1/2 hour settling down, no conversation, no cell phone, non-stimulating TV,

I used to watch a music video that grabbed both my auditory and visual attention in a mild manner. maybe a repetitive music or video that does not excite you. As soon as you feel a sleepy sensation, quietly get in bed. If something triggers you awake, get up and get settled into sleepy again then go to bed. Lying in bed fighting wakefulness is counter to getting to sleep.

When PCS causes insomnia, it can take work to find a system that works.

I found my best posture was flat on my back with a pillow curled up around my ears. It provided that sensation against my face that helps me drift to sleep. I learned to sleep on my back by sleeping in a recliner with a pillow curled around my face. I had shoulder trouble so I had to learn to not roll onto my shoulders. Learning to sleep this way changed my life. I usually fall asleep in minutes and sleep soundly until I naturally wake up, often in the same position. A sleep therapist who presented to my brain injury support group said this is the best sleep.