The German chancellor's body shook visibly as she stood at a military honours ceremony alongside the Finnish prime minister in Berlin.
It followed similar episodes on 18 June and 27 June. As in both those cases the 64-year-old recovered quickly as she started walking.
The first incident happened in hot weather, and Mss Merkel said afterwards that she was fine after drinking three glasses of water.
The weather was cool at the latest event.
Ms Merkel said as she attended the G20 summit in Japan on 29 June that she understands questions surrounding her health, but insisted: "I'm fine."
More about: Merkel