im not sure if this is actually the problem, but it always works when i do this.

sometimes my car wont start... dash lights turn on, but engine wont start. all i do is wiggle that wire and then the car starts right up. is it actually a problem elsewhere and that wire is just a coincidence or could that prong be loose inside the starter?? can it be tightened or resoldered??

 

from the picture it just looks like a negitive cable to your starter

to fix it just try to tighting that down (both ends)
or replace it (there pretty cheap)

good luck