My 2008 e320 cdi Sport has developed a starting problem. Only ever from cold. It started turning over more than it used to and then once warm is fine. Today however it didn't start after three attempts I left it for an hour, it then started at the second attempt. It has 113,000 miles on clock, has had 7 MB dealer services in 4 years from new. Any ideas , it kicks out a load of White smoke too from cold. On the road it performs as always, pulls great and never misses a beat. I understand the EGR valve may need replacing ???? Any suggestions gratefully received, not sure how much this will cost to replace ?!?!?