Does ur car do anything funny when the warning lights come on? Could be anything from faulty coilpacks to O2 sensor etc...best way is to find a workshop with a Nissan Consult machine, they plug it in your car and will be able to pinpoint what the error is and what needs replacing.
There is a thread on here that teaches you how to do it urself but if ur not game, then leave it to the experts but definately get it looked at quick smart.
Mine did this too when I first got it, turned out it was a faulty o2 sensor..