E420 Smokeing on start.. sometimes on 1997 Mercedes-Benz E420

My 1997 E420 with 134k miles on it will sometimes blow a small puff of white smoke when I start it. Only every now and then so I have no idea of the logic there. I noticed the other day when I had to really punch it merging onto the interstate that same small puff of smoke came out the tail.
My mechanic pulled the covers and said all the oil paths are clear and the diagnosis is that I need new valve seals at an estimate of 2100.00. I do love my car and it looks like the day it came off the factory line so I won’t mind repairing it, I just wanted to make sure there aren’t any other suggestions out there. I have always had the scheduled maintenance done by dealership and use synthetic oil. I am really surprised of this problem on what I still consider a low millage vehicle; my last benze a 300 is still running no problems with over 300K miles.

Additional info, I am not loosing any water but am burning about 1qt oil per month. I use synthetic MobilOne 10w-40 oil.

Asked by for the 1997 Mercedes-Benz E420
White smoke may indicate water leaking into the cylinder, from a leaking headgasket or cracked head/block. Are you losing engine coolant? Can you have your mechanic check for a leaking headgasket?