Wake up suddenly to a sudden “pop” or “white light”?

I’ve experienced something very similar.....a sudden loud pop or flash of light when waking up. In my case, a doctor explained it as a sleep‑related parasomnia called Exploding Head Syndrome. It’s harmless but definitely scary. Since you’re dealing with post‑concussion symptoms, it’s good that you’re already scheduled for a sleep study and following up with your doctors. You’re not alone in this, many people have had these episodes, and talking with a sleep specialist can help you understand what’s going on. For me though what scared me more than the symptom alone is it was part of a constellation of other sleep wake neurological symptoms, catastrophic total insomnia, REM sleep without atonia, dream intrusions, visual distortions, involuntary movements, cognitive slipping, somnambulism, mild gliosis, elevated WBC, hypertension I was having: the fact that they were happening together while I struggled to find anyone willing to evaluate the medical side of what I was experiencing. Being routed toward psychiatric care without a full medical workup left me feeling unheard at a time when I needed clarity the most. At times, it felt as if the Plummer Building’s doors had closed just as I was reaching for help. I am glad those doors are still opened for you.