this happened to me as well on my 190e2.6, and as it happened to me before, so I knew what to look for.

Previously, the indicator bulb had burned out and I had to replace it. This time it was a matter of just re-seating the bulb in its carrier - some oxidation probably formed at the contacts.

the quick-blinking behavior is to tell you that one of your (front or rear) indicator lamps is not working, but you have to be aware as well that you are probably not signalling your intentions to the other drivers. This is one of those things you take for granted but get really insecure about when it is gone ... as such, I carry extra bulbs in the trunk ...