Any ideas what could be wrong with my ford mondeo?

Just wondering if anyone had any ideas as to what could be wrong! I've got a 2001 ford mondeo and it runs fine apart from feeling a bit bouncy when driving. i had the wheel balancing checked but it still does it. And the other problem is that every now and then it cuts out, and as soon as i start it up again it runs fine and then goes days/weeks without doing it again. A few people have said to change the spark plugs and leads, is it that simple??