i have a 230e.. same sound. due to replace the valve lifter with play.. just don't know anybody in my area who can fix it for a reasonable fee. you are so lucky you are able to diy this repair.
I have a similar issue on my W124 230E. Occasional hard starting, misfire and noisy lifter when starting from cold (losing oil when valve is compressed). I thought of replacing only the one, then again, they've all done the same mileage and at less than USD70 for a full set I thought I'd replace them all.