Only two things I can think of,.. that would would cause this...
... a slowed flow from the petcock... that starves out the engine, given time...
... a slow leak in a float, just above the full fuel level,... that only begins to take on fuel, as the float level drops low enough to expose the leak...(but has time to evaporate out, and raise the float above the leak, after sitting)...(that's a stretch)...
I'd pull the petcock first, and look for some clogging on the pick-up tubes... (just 'cause it's easier to check)....
With 102 posts.. either we suck... or you have a very unusual problem...
... but we're stubborn... don't give up...
At this point,.. we absolutely must find out what's going on...
We're with you in spirit...
...
PS... if it's neither of those...(... and I don't have time to read back over all 102 previous posts)...
I'd start looking for an electrical, overheating component...
JMHO...
Best of luck...
...