I've been chasing starting gremlins for a long time. Delayed, slow, or grindy starts happened randomly, but they never left me stranded so I kept putting them off. I finally traced it to the clutch safety switch. This is a quick and easy check if you are having similar issues. You just need a small knife or screwdriver to pry off the clips and some alcohol or electrical contact cleaner.
Unclip the switch, remove the connector, and pry off the rear cover.
The contactor is symmetrical, you can simply pull it out and turn it around. Its like a whole new switch.
Clean it all up if you want and put it back together.
In my case it was so used (200,000mi) that the rubber button on that pushes on the plunger was loose. So I added a washer from my big-bag-o-random-crap to the back of it to close the gap.
And now I have a happy starter.