starter problem, please help!

hi everyone, my starter is loose i think. most days when i try and start tmy 95 escort gt, and i turn the key to start it, the power cuts off and dies. so i gotta pop the hood, and pull up on the positive side of the battery i think (a cable) and the everything suddenly lights up. i tried jamming the cord down but that only worked for a few days. im guessing a nut or something is loose cause if i pull a connection is still being made. can i fix this just by going under the car? i have no idea what it looks like... i heard u can sqeeze under there. please help any help would be awsome!