2012 Isuzu D-Max: Engine making noise

My 2012 Isuzu D-Max has developed a noise in the motor, even though it's only done 11,000 km. It rattles for a few seconds after it's started first thing in the morning or after it's been sitting for a while, but the noise then goes away. It sounds as if it's coming from the valve train. Is this a common thing with diesel motors?