Hello all,

Here's a mystery that I'd like to solve. Or if, it's normal for my old Benz, I'll deal with it.

About 80% of the time, my car idles very nicely. It starts a little rough, but after about 5 seconds it's surprisingly smooth.
20% of the time, however, I'll come to a stop and it will be a bit more 'rumbly' and have more shaking in the cabin. I haven't detected any pattern to when it happens, and it's not that bad, but noticeable.

I thought at first it was air in the fuel system, but I don't have any fuel leaks that I can see.

All engine bay fuel lines are new (except for the cloth-covered return lines)
Fuel filters are new
I did a recent diesel purge
Air filter is new

Any ideas?
82' 300D