first you need to buy a good manual for your year model car read it concentrate on the ignition chapter then buy a spark tester at any auto parts store or you can use a known good spark plug . when your acts up again pull off nbr. 1 plug wire and plug in your spark tester making sure the outer case of tester is grounded to sound grounding point then have someone start the car as normal while you watch your spark tester (don't touch it!) if you do not have spark at the tester than your problem is in the ignition circuit it could be a bad coil,ignitor hall effect switch (pickup) or No power getting to the distributor/ign. circuit your manual will have methods of testing all of these items.I belive advance Auto can test your ignitor .If you have spark at the tester and the car still does not start and run than your problem is some where else .i would check the compression of each cylinder to eliminated this as a cause.which is unlikely the problem just for the fact that it does run at times and not at others but this will give you a good base line . Next then you can read some more and trouble shoot from that point your manual will have a flow chart on what to check next follow it .a general rule is find what is working correctly and keep looking until you find the part or parts that are not operating correctly this will save you alot of money . because you will end up finding and replacing only the bad part instead of using the shotgun method of trouble shooting if you need any more help just ask -MC1