Hi, I've had my DC5 for 3 weeks and have just noticed the same thing...... It's happened the last 2 times I've started the car up (both cold mornings, and after the car has been sat for a couple/few days) - it's a very short sharp sound. In addition, a belt's squeaking for a few minuites after starting, and until the engine has warmed up. Looking at what the other replies said, and the fact the belt on mine squeaks a bit too.....it sounds like it's happening because the belt is loose. boz5r - Does the belt on yours carry on squeaking for a while as if it's loose?