After travelling 20 km my 2004 Nissan Pulsar stalled while stopped at traffic lights. It took two goes to get it started again, then no problems. I drove a further 25km and was fine, but this is the second time it has happened. The first time was in traffic, but it started again straight away. The car has only done 177,000 km and is serviced every 12 months because I only travel about 5000 km per year.
It would be worth having a mechanic check it for you. It could simply need a tune up, new plugs, plug leads, clean of the throttle body, or idle adjustment.