2003 Ford Escort Sometimes my car won't start.

I just got all my fluids checked up on my car and I'm getting my serpentine belt fixed soon. Every once and a while randomly my car won't start. It makes a click like its trying to turn over but it won't. Then later it will start working again and won't have any problems. (Over the weekend it wouldn't start but this morning it started right up with out any problem.) My buddy told me it was a starter cable wire. The wire he points to is black with a yellow stripe located behind the battery to the right hand side. The wire in question is clamped to the car and is stripped, exposing the copper in the wire. Sometimes if I mess with the wire a little the car will start up again. I went to autozone and was told that I can only get this part through a dealership. Does this sound like this would be the problem? If so what is the name of the wire I'm trying to replace? When I look for it online I can't find it by searching "starter cable wire." Thank you.