A 26-year-old Harlem man died in police custody a short time after he had been behaving erratically, authorities said.

Anthony James was spotted by cops “acting erratic and lying on the roadway” around 2 a.m. Saturday, in the vicinity of West 151 Street and Frederick Douglass Boulevard, police said.

He then ran from officers, climbed on top of a moving car and rode it for about two blocks before jumping off, police said.

Cops nabbed James and called EMS but he lost consciousness before paramedics arrived. Naloxone was administered, police said.

James was later pronounced dead at Harlem Hospital and the incident is under investigation.