German Chancellor Angela Merkel was seen trembling once again during a ceremony in Berlin on Thursday, eight days after a similar incident.

Video showed Mrs Merkel, 64, gripping her arms as her body was shaking on Thursday. After about two minutes, she looked steadier and shook hands with the new justice minister.

She was offered a glass of water, but did not drink it.

Mrs Merkel had blamed the previous incident on dehydration.

She later set off for the G20 summit in Japan as planned at lunchtime.

"All is going ahead as planned. The federal chancellor is fine," spokesman Steffen Seibert said.

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German news agency DPA said that despite the spell of very hot weather it was cool during the ceremony in Bellevue Castle, where President Frank-Walter Steinmeier was presenting Justice Minister Christine Lambrecht.

Last time, Mrs Merkel trembled while standing next to Ukraine President Volodymyr Zelensky in the hot sunshine. She said she had felt revived after drinking some water.

On Thursday she attended Ms Lambrecht's inauguration briefly in parliament - the Bundestag - then left.

When she returns from Japan, Mrs Merkel faces tough negotiations in Brussels on Sunday when she and other EU leaders meet to find a candidate for the powerful post of EU Commission president, a replacement for Jean-Claude Juncker.

On Wednesday, Mrs Merkel appeared to be her usual self in the Bundestag during an hour-long debate, and later gave a speech at Berlin's Humboldt University.

What could be wrong?

Government sources told German media there was nothing to worry about and, as she left for Osaka, her spokesman tweeted that she had "numerous bilateral talks planned with other heads of state and government".

However, Mrs Merkel did have an earlier bout of shaking in hot weather on a visit to Mexico in 2017, as she was attending a military honours ceremony.

She was given thorough medical checks and nothing was found to be wrong, reports said. There was no evidence, for example, of Parkinson's disease, for which uncontrollable tremors are a symptom.

Asked by the Focus website what might be wrong this time, leading Bavarian GP Jakob Berger said she would need to be checked out as soon as possible. He ruled out Parkinson's disease, as the trembling had been too pronounced. But he said "if she were my patient, I would definitely clarify the symptoms before the trip (to Japan)".

Another health specialist, Dr Christoph Specht, told German media that the chancellor may have contracted an infection, as shivering indicated an infection that was flaring up again. An infection was potentially the cause of something else, he said, and Mrs Merkel would need to be checked out.

What medical care does Merkel have?

The chancellor does not have a personal doctor, DPA reports, but she does have easy access to top medical care. Her office is right near the Charité hospital and the military hospital in Berlin, and the head of the chancellery is a qualified intensive care doctor.

A government spokesman refused to comment on any care she may have had, but it is likely she will have access to medical care on her trip to Japan, as a foreign ministry doctor always accompanies German delegations on major overseas visits.

Mrs Merkel is now in her fourth term as chancellor, a role she first began in November 2005. She has said she will leave politics when her current term ends in 2021.

She has been in good health while in office, and even worked from home after a knee operation in 2011; she suffered a fall while skiing in 2014. Her absences were only brief on those occasions. Her mother died earlier this year.

If she were found unable to fulfil her duties, Vice Chancellor Olaf Scholz would step in. He is currently the finance minister, and is in the centre-left Social Democratic Party (SPD), the CDU's coalition partner.

She has a reputation for remarkable stamina – during intensive late-night discussions at EU summits, for example.

She is Germany's third-longest serving post-war chancellor. The record was set by her centre-right Christian Democrat predecessor, Helmut Kohl (more than 16 years), and the second longest-serving chancellor was Konrad Adenauer (more than 14 years).

BBC.COM