It sounds like you may have some teeth missing on the flywheel. If you have someone remove the starter and crank the engine it will turn the flywheel and you should be able to see where the teeth are missing. If the flywheel has to be replaced most likely the transmission will have to be removed to do this.
Before you do anything, you should make sure to take the vehicle to an ASE certified technican only. These technicians go through intensive training and testing to become certified. You can find a certified technician near you by going here:
〉 Answered on Dec 15th, 2006 by Lori Johnson, Owner and Instructor at Ladies Start Your Engines