I Have Days Where While I Am At Work I

I have days where while I am at work I seem to have times that i have a sort of fuzzy head, and there are times when I have trouble staying focused, get confused where I am in the process that I am working, loosing my place and getting confused. also i can feel like i am going to fall asleep however if during my lunch i go to my car and lie down i feel better afterward but i am not tired enough to go to sleep.