The shuddering could have a number of causes, potentially being the result of a misfire that disappears as the engine warms up. This misfire could be caused by faulty and/or dirty spark plugs, or faulty high-tension leads. There may also be problems with the fuel delivery system, such as with the fuel injectors or the automatic choke. To pinpoint the problem, this will need the attention of a trained mechanic so the issue can be isolated and fixed. In any case, fixing the misfire will make your car more efficient and much better to drive. As an RAC member, your vehicle can be booked for a 30-minute free fault diagnosis check. To take advantage of this benefit, call 13 17 03 to make a booking.