And to start with, to eliminate all the easy causes, I would:
1. Change all your spark plugs (use NGK).
2. Check the condition of your distributor cap and rotor button. Clean all the internal contacts with some fine wet and dry sandpaper. Replace them both if they look too far gone.
3. Whilst you have the dizzy cap and rotor button apart, pull the cover off of the cam position sensor and check for any oil contamination in there. If necessary, clean it all up with a can of electrical contact cleaner.
See if that cures any issues..... If not, look up the procedure in this site for checking the ECU for any fault codes and take it from there.
Cheers, Dan.