What in the world is causing my symptoms?

every once in a while i will start to sweat really bad but i will have goose bumps, i will get dizzy, my hands will shake really bad and i feel like i'm going to pass out, usually after i eat something i will start to feel better. i have had blood work before but the doctor said everything looks normal. this just happened while i was at work and i went to the snack machine and ate something and after about 10 minutes i feel back to normal. what is going on? i ate breakfast this morning and i'm not on a diet or anything.