2003 Vauxhall Zafira Jerking !!!!?

I have a 2003 Vauxhall Zafira 1.6. The car has done 40,000 miles. The problem i have, when travelling along at a constant speed, for example 40 mph, all of a sudden the car will jerk. Is this the EGR Valve. I have no Engine management light on, to indicate a fault. Atb Mark