Diesel? Could be the glow plugs warming up before the engine fires. In a diesel, you need to turn the key to the start position, but not start the car until a light in the dash goes out to tell you the glow plugs are hot enough to ignite the fuel. If there is no light, you need to wait about 5 seconds before you turn the key all the way.
GM diesels in cars, man that's WAY back!!
