I suspect this probably varies across the entire population to some degree, but for me it feels like my senses and my mind aren't fully "bound together" properly when I wake up, and it takes a while of being conscious, QUIETLY, for them to come together and be functioning right. This process takes far longer if I'm in a state of serious/chronic burnout, up to several hours.

If I skip it and jump directly into activity, things usually stabilize quicker, but in a crappy muddled way, and much of my day can be off, I feel dumber, forget things, lower threshold for confusion/distress from random events, etc.