Check the two little o-rings on the end of the shaft on the oil filter housing cover -- no one ever seems to change these, and they get old and hard and leak. Oil leaks down from the lifter galleries over night, allowing the lifters to go "flat", and they rattle when you start up.
Cheap easy fix, much better than a camshaft or new lifters! -- cured the noise on my 87 300D.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!