Stratus 96 starting problems

I have a 96 Stratus that starts fine when

1. The car has been off for extensive time (overnight)
2. The car has been off for very short time (15 minutes)

However, the car takes about 10 - 15 sec to start when has been off for about one-two hours. The engine is not completely cold.

I changed the plugs and while I can see an improved overall performance of the car, I still have the same problem when starting after intermidiate time off.

Any help will be appreciated.

Regards..