Why wake my brain but leave my body paralyzed?Understanding the glitch behind waking nightmares

From the show

Oh, god... really?

Your brain sometimes wakes up from REM sleep before deactivating the chemical lock that keeps you from acting out dreams. This synchronization error leaves you fully conscious but completely unable to move or speak. Attempting to interpret this helplessness, the mind often projects hallucinations of intruders or heavy pressure, turning a simple biological lag into a terrifying ordeal.