Are you saying that the problem is heat-related - that is, does it occur only or almost only when the weather is warm or the engine is warm? And is it the case that once started the engine doesn't stall? When the engine is running do the various electrical devices in the car work properly (lights, radio, defog, etc)? If these are true it makes the starting circuit a near-certainty.

If so - tracing the connections with a multimeter is really the way to solve it, but many questionable electrical connections act up when warm because the resistance of common materials increases with heating. Sometimes the surface of the connections looks ok but there is corrosion just beneath - especially battery, primary alternator, starter terminals (those that carry lots of current). Those could all go bad only when hot.