Join Date: Feb 2011
Location: Colorado Springs, CO
Unusual, but you may have provided your own clues.
The underhood fuseblock is essentially 3 massive connectors from those boxes to the rest of the car. The center bolts hold those tight. Confirm they are tight. If not tighten them up. Generally, they are trouble free.
If they are already tight, I'd pull that fuseblock and look for some signs of heat damage or anything that would indicate box warping and giving a poor connection when hot.
I've seen it on other cars where a specific circuit has worked loose. I'd concentrate on the section of box with the starter circuit.
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