You turn the key and just get a labored chug-a-chug-chug from the starter motor. Finally, the engine turns over and catches, but you know it shouldn't be that hard.
That symptom could be alerting you to one of several different problems lurking under the hood. One unpleasant possibility is that one or more of the car's spark plugs have become coated with oil. This can happen if the valve cover gasket or any grommets sealing off the valve train from the spark plug holes is leaking. If it is, then oil being splashed about inside the valve train is also escaping to foul your spark plugs.
The fix doesn't have to be expensive -- clean the fouled spark plug(s) with a degreaser solution and replace the valve cover gasket(s), making sure to torque the cover down only to the manufacturer-specified pressure. Any tighter than that and you could create an oil leak all over again!