“I am up for Shavuos but not the whole night. I don’t like to daven like a zombie.”
Don’t mean to attack, but aren’t you davaning to Hashem, which he himself would want you to stay up all night?
Where does feeling like a zombie come into the picture?
If your excuse is because it’s hard to stay up then fine, but blaming it on Davaning doesn’t make sense. (Unless there is some heter)
All this assuming you are a male