99 Merc Sable DOHC, car cranks but engine will not attempt to turn over / start

What is your question?

After making the final stop while running errands on Monday, my car's engine had a "rough" start. It took about 2 seconds for the engine to stabilize. Once it did the car ran fine and I drove it home w/o any problems. The car then sat on the driveway for a few days, during two of which we had below freezing temperatures (not sure if it makes any difference here). When trying to start the car for the first time since Monday, the car cranks but the engine does not attempt to turn over or start. The battery is good and I didn't see any warning lights when trying to start it. The only noticeable sound was the starter(?) cranking over and over again.