It came hours before Merkel was due to board a plane for the G20 summit in Osaka, Japan.
Angela Merkel was seen shaking at a public event for the second time in less than two weeks as she stood alongside President Frank-Walter Steinmeier at a ceremony in Berlin. "The chancellor is doing fine".
Germany is now experiencing a record-breaking heatwave that has engulfed much of Europe.
Asked about Merkel's latest shaking episode, Interior Minister Horst Seehofer told reporters: "I won't comment on this". A spokesman on Wednesday dismissed any concerns over her health, saying "the chancellor is fine". German privacy laws are very strict on that type of information.
Last Tuesday, Angela Merkel was seen shaking repeatedly as she stood next to Ukrainian President Volodymyr Zelensky during a red-carpet ceremony outside the chancellery, while a military band played their national anthems.
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She later said she had forgotten to drink enough water during the hot weather at the time, but that she felt better after having three glasses.
This was not the first time Merkel has been seen shaking under similar circumstances in the hot sun, according to the dpa news agency.
Standing next to Steinmeier as he addressed the gathering, Merkel started shaking visibly in her upper body, then crossed her arms as if to brace herself.
She has a reputation for remarkable stamina - during intensive late-night discussions at European Union summits, for example.
Merkel began a stage-managed gradual exit from politics in October, when she said her fourth term as chancellor would be her last and that she would not seek re-election in 2021, when the next federal election is due.