It's not a collapsed hydraulic adjuster. That happened to my erstwhile '84 190E 2.3. It made a continuous clacking noise, and I knew what it was right away because I was familiar with the design. It was replaced on warranty by the dealer.

Very rarely on my '88 190E 2.6 I'll hear a lifter ticking for a couple of seconds after a cold start although it rarely sees temps below about 40F.

Be sure to use CJ-4 or CK-4 engine oil, which is the best modern oil to use in vintage engines with sliding surface valve trains. It's also is richer in detergents/dispersants than SN to help keep lifters clean; 15W-40 is okay for cold starts down to 15F. If typical winter lows are lower, use the 5W-40 "synthetic" version.

Duke