Question: what does it mean when you wake up groggy?
Answer: Gartenberg: When you wake up, you have something called “sleep inertia.” It can last for as long as two hours. That's why you get that groggy feeling, and if you're sleep deprived, it's going to be worse, too. Studies also show that if you wake up while in deep sleep, you're going to have worse sleep inertia.