The defendant, identified as Josef S, is charged with 3,518 counts of accessory to murder.
He is alleged to have worked as a guard at the Sachsenhausen concentration camp near Berlin between 1942 and 1945 as an enlisted member of the Nazi Party's paramilitary wing.
Josef S's lawyer, Stefan Waterkamp, told the court that his client did not want to comment on the allegations, according to German news agency DPA.
He said his client 'will only provide information about his personal situation'.
Thomas Walther, a lawyer representing several camp survivors and relatives of victims, said he hoped Josef S would change his mind.
"A man is not made of stone, not a machine," Walther told AFP.
"Maybe he will still say something."
Despite his advanced age, he is considered fit enough to stand trial, although the number of hours per day that the court is in session will be limited.
Prosecutor Cyrill Klement told the court: "The defendant knowingly and willingly aided and abetted this at least by conscientiously performing guard duty, which was seamlessly integrated into the killing system."
More than 200,000 people were held at Sachsenhausen between 1936 and 1945, with inmates often dying from starvation, disease, forced labour, medical experiments and more.
Others were also killed in the SS' systematic shootings, hangings and gassing.
The exact number of deaths is not known, but some say it could have been as many as 100,000 - while experts suggest figures of 40,000 to 50,000 may have been more accurate.
Leon Schwarzbaum, a survivor of Sachsenhausen, attended the trial as a visitor.
The 100-year-old, who also survived the Auschwitz death camp and Buchenwald concentration camp, told DPA: "This is the last trial for my friends, acquaintances and my loved ones, who were murdered, in which the last guilty person can still be sentenced - hopefully."
The trial of another suspected former concentration camp worker was held up last week when the 96-year-old skipped the opening.
The woman, believed to be a former secretary for the Stutthof camp's SS commander, was tracked down within hours, and proceedings are now due to resume on 19 October.
Christoph Heubner, the executive president of the International Auschwitz Committee, said in a statement: "It shows an incredible contempt for the rule of law and for the survivors, too.
"[Authorities] should have reckoned with an escape and put the care home under guard and brought the accused to the trial."