They can get pretty damn hot.. especially this time of year, depending on your location. Yes on checking resistance, both when cold and hot. If you notice a big difference, it might be your problem.

Alternatively, carry some water around. Next time it acts up, pour water over the coil to cool it, see if that gets it going right away.

Honestly though... I do rather suspect a fuel issue. Specifically vapor lock or fuel boiling in the carb floats.

Try unlatching the hood on these really hot days. That'll make a gap at the back of about 3/4", which will do lots to keep under-hood temps lower.

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-Matt I ♥ my ♂