I am having a problem in the morning starting the engine of my Polo 1.9 SDI 2000. I have to attempt 2-3 times to start it and after it starts, it makes a strange noise and throw out smoke. I checked the engine heaters (all are OK). In the same day if I let the car rest for 10 hours, the car doesn't have trouble starting; it start on the first attempt. I also checked the oil; it has enough (I use 10w40). Any idea what the problem might be or where to go next?