I got the error code 6 too. I visually inspected the sensor and found a lot of crud in the connector. Tried to clean it out with some compressed air, but that didn't help. Was going to replace the sensor but haven't gotten to it yet.

After I got the error code 6, I came upon this theory: If the ECU is getting a water overtemp reading (whether legitimate or not), does the ECU prevent the car from starting? If so, that would explain making the car hard to start until it "thinks" its cooled down sufficiently.

I've also heard to check the ignitor in the distributor. That's also on this weekend's to do list.