According to BBC History, Sir Isaac Newton died in his sleep as an old man on March 20, 1727, at the age of 82. Prior to his death, Newton was living in Kensington, Middlesex, England.
After he died, an autopsy showed that Newton had traces of mercury that were still active in his skin and hair, which was likely the result of his alchemical research that involved mercury use. Newton was highly eccentric in the time before his death, according to his peers and family, and extended mercury poisoning may have been part of the reason for that. It is unknown whether mercury contributed to his death.