Long Crank on 2003 Mazda Mazda6

Just bought me a Mazda 6 -03
Sometimes, about every 5th time I start the car it needs some extra long cranking before it starts.
I thought cleaning the MAF-sensor would fix the problem but no..
According to the service manual, the spark plugs where replaced recently.
Anyone who can give any suggestions on what the cause could be?

Asked by for the 2003 Mazda Mazda6
Sounds like you have a starter problem, if the starter is good it could be the Teeth on the flywheel