IMHO it's fairly common on ALL CIS Benzes. A few seconds is really no big deal, I even remember reading something on a diagnostic fiche (years ago) for M116/117 engines about this being "acceptable".

Assuming everything else is OK, you probably have a little internal bleed-off somewhere, like a fuel accumulator or even a fuel distributor. At high ambient, and with a hot engine, the fuel will vaporize more readily, especially with a loss of system pressure from a small bleed-off. This may be why you only notice it at warmer ambient.

I wouldn't worry about it too much. If you *really* want to get into it, testing the system for internal leakage is pretty straightforward.

Cheers