98 Honda Civic shaking, car loosing power

I have a 98 Honda civic, 100k, manual transmission. Recently it has been acting weird. The car will shake and the RPM gauge goes up and down and make the car shake. Sometimes it even dies, when I try to start it, it will start but dies again.
I took it to different mechanics but none could figure out the problem. I finally took it to a Honda dealer after my check light engine went on. The check engine light was to change the Catalyst converter, and he said it has nothing to do with my problem. The Dealer said I need to change the spark plugs, wires and ignition switch. I did all that but the problem is still there.
Can anyone help me out?
P.S: the starter, coil, distributer are all working fine. Also while being in the mechanic shop, the car didn't want to start, so he found out that distributor won't spark, but it started the next day!
Thanks!