Sounds counterintuitive but I remember occasionally felt sleepy whenever I drank coffee... doesn't relax me at thesame time though.    I suspect the coffee was reacting badly with another foods/substances in my body and making me feel tired, sleepy, weak, headache, etc, Other times the coffee works as expected - made me awake and active.

I do not depend on it these days to keep me awake. I naturally stay awake and active without the help of things like coffee, unless I task my self more to do things when it want rest.