Hi, I Just Woke Up From A Nap And As

Hi, i just woke up from a nap and as soon as i stood up i started feeling so weak that i couldnt stand any longer, my stomach was also turnng and i felt slightly nauseous. I have now gone back to lay down and i dont feel it as much any more, only when i stand up and walk. What is wrong with me? Why has this come on all of a sudden after a short nap?