Johann Rehbogen is accused of complicity in mass murder at the Stutthof camp near what was then Danzig, now Gdansk in Poland.
His trial opened on November 6th, but after several hearings was adjourned as Rehbogen's health deteriorated.
Fourteen hearing days had been set for Rehbogen's trial but on Thursday a medical expert found it unlikely the defendant would recover from his current health problems, a court spokesman said.
A doctor is due to re-examine Rehbogen in January, and will advise the court on whether he is fit for trial.
Judge Rainer Brackhane would then decide whether to restart the trial with new hearing dates or scrap the case.
Under Germany's court procedures, trials have to be restarted if hearings are halted for more than three weeks.
Rehbogen was aged 18 to 20 when he served as a guard from June 1942 to September 1944 at the Stutthof camp.
The German, from the western district of Borken, North Rhine-Westphalia state, is charged with being an accessory to the murders of several hundred camp prisoners.
These included more than 100 Polish prisoners gassed in June 1944 and “probably several hundred” Jews killed from August to December 1944 as part of the Nazis' so-called “Final Solution”.
If found guilty, he faces a sentence of up to 15 years in prison. Given his age and the possibility of an appeal he is considered unlikely to serve any time behind bars.
He broke down in tears at the trial opening and subsequently told the court he was ashamed of having been in the SS.
Rehbogen however insisted that he was unaware of the systematic killings at the camp.
Germany has been racing to put on trial surviving SS personnel, after the legal basis for prosecuting former Nazis changed in 2011 with the landmark conviction of former guard John Demjanjuk.
He was sentenced on the grounds that he served as a cog in the Nazi killing machine at the Sobibor camp in occupied Poland, rather than for killings or atrocities linked to him personally.
German courts subsequently convicted Oskar Gröning, an accountant at Auschwitz, and Reinhold Hanning, a former SS guard at the same camp, for complicity in mass murder.
Both men were convicted at age 94 but died before they could be imprisoned.