system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why does it seem to take a long time for me to become "fully functional" after waking up every morning?

When I wake up my brain feels really groggy for a while.  My legs don't want to take fully steps. Unless I have someone engaging me with something very important immediately, I basically feel like a zombie moving around autonomously. Note: I have been diagnosed with sleep apnea, but have not been able to afford to do anything about it.
gpt
This is known as sleep inertia. It describes impaired cognitive functioning which many people experience when waking up. There are a variety of reasons why it happens, including the binding of certain chemicals to brain receptors upon waking up and decreased blood flow to the brain.

The effect can be magnified if one wakes up during the stage 3 (slow wave) stage of the sleep cycle or if one wakes up during the circadian nadir (around 4am).