I would star with the basics, spark plug renew them or clean them and regap em, chekc ya gettin strong spark when engine is runnning remove a lead and put it close to the block it should produce a straong regular spark, try this on all 4 but do em one by one, i f you remove a lead and engine idles the same then the problem could be with the plug on that cylinder, this time of year damp HT leads are a big problem so think about replacing them too.
What engine is it

Get into the car in the morning and try to turn it over, it seems very sluggish on turning over, then when it does it somethings devolps a fault, i can floor the throttle and then all of a sudden it will lose all revs, whe driving along it sometimes does this but as soon as you change it stops. The stereo etc are all working fine with the ignition on ! anyone got any ideas on what it could be