My problem was...
"The main problem I have with starting it after not using it is that the engine cranks erratically. By that I mean that it will turn a couple of times, stop for a couple of seconds, stop again, etc. (all the while holding the key on). I then stop for a minute or two to let stuff cool down, then try again."
The solution was a new starter.
The bushing in the old one didn't *look* bad but when turning the spindle by hand, you could definitely feel the eccentricity.