The clatter is a very distinct noise that sounds like, well, low oil pressure on moving parts. It happens on cold starts, and lasts just a few seconds. Get in your car, turn off the stereo and the ventilation fan, roll down the windows and wait for the buzzer to stop, then start it up. If the starter noise and the engine firing makes you smile, then you don't have a problem! Mine has the clatter and lifter noise as well. Note I just switched to Mobil 1 with the timing chain replacement.
I'm not so sure the clatter is always the timing chain. I just had mine replaced, including the upper tensioners, and heard the noise again 1600 miles later. There is a post here somewhere that suggests that the variable valve timing gear will be noisy until oil pressure builds, and that the check valve in the oil pump(?) or in the oil filter housing(?) is there primarily to keep the top end pressure up when the engine's off. Also, in the same post, a service bulletin was referred to on replacing o-rings on the lifters with upgraded parts. I'm bringing mine back in at 105K to get it right. Anyone have any other ideas?
1995 E320 Wagon Moonstone Grey/Parchment 106K mi.
2007 E63 AMG Graphite/designo 75K mi