Citroen Saxo car juddering? as if misfireing?

my car keeps juddering as if it wants to go and when it does this the sound is like a pop pop noise.. mainly does it when it is cold but recently doing it more, sometimes its so bad it feels as if it is going to stall like a manual, touchwood hasnt happended yet and hopefully doesnt! people have told me that it sounds like it is misfiring but i have no warning lights and only does it occasionally but as i say this its doing it more and more any ideas of what it is? i have been told maybe spark plugs and leads or maybe coil pack if its not these problems what isit?