Born in Brooklyn, New York, Warren described his childhood as quiet and uneventful. His father ran a chemical company in Brooklyn. He had no inclination to make films, and although there was an 8mm camera around the house, he never used it.

When he was 15, he started going to the Bleecker Street Cinema. One day, during a screening of Potemkin and L'Avventura, Sonbert found a large manila envelope sitting on the seat next to him, full of issues of Film Culture, Films in Review, and other film magazines. He took them home, read them, and began seeing even more films, perhaps twelve times a week.

When he was 17, Sonbert met Gregory Markopoulos, who loaned him his Bolex camera, and encouraged Sonbert to make films. They also became lovers for about six months; Sonbert later called Markopoulos his first love.

His early films were basically diaries: lyrical records of his friends going through their lives, involved in daily occurrences, shot without pre-planning. They were almost always accompanied by rock songs of the period, whose energy added to the power of their rapid editing. The core of Sonbert's early craft is that he created, without complicated camera choreography, editing, or a pronounced story line, films that produce a heightened emotional state.

After he became a filmmaker, he said that his true introduction to cinema was his viewing of Alfred Hitchcock's Vertigo when it first opened; totally infatuated, he saw it multiple times, and much later wrote opera and classical music reviews for The Advocate under the pen name of Scottie Ferguson.

Attracted to the work of Howard Hawks and Alfred Hitchcock, Sonbert wrote an angry letter to the manager of the Bleecker Street, protesting that their work was almost never shown there. Surprisingly, the manager wrote him a letter back, and as the months went by they became good friends. Sonbert got a job as usher at the Bleecker Street, but he spent most of his time meeting filmmakers through the manager.

Although he shot a couple of 100' rolls of 16mm film, Sonbert was still reluctant to begin filmmaking, feeling himself inadequately tutored. To rectify this, upon graduation from high school Sonbert enrolled at New York University to study film. In his second year at NYU, Sonbert made his first 16mm movie, Amphetamine, an early gay-themed filmed centering around the lives of two friends of Sonbert's who shared a predilection for injecting speed. The film was screened publicly at the Bleecker Street for a number of critics and filmmakers who were enthusiastic in their praise of the film, and Sonbert's career was truly launched.

This film was followed by Where Did Our Love Go (shot in June, 1966) a 15 minute color film with a taped soundtrack. Next came Hall of Mirrors (shot in October, 1966) a 7 minute film in color and black and white. Sonbert now began to carry the camera with him as he went about, shooting whatever seemed to him to be worth recording.

Sonbert also had screenings at the Jewish Museum and the Elgin Theatre, as well as appearing with his work at the MIT Film Society in Cambridge, Massachusetts. With this money, and a graduation gift from his mother, Warren left the country for Morocco in April of 1969; he was to receive family money throughout his life. Before leaving, he withdrew almost his entire work from distribution. It was re-released in the early 1970's.

Sonbert moved to San Francisco in 1970. Soon after moving to San Francisco, he identifying himself as gay. He traveled frequently to New York, accepting a description of himself as "bi-coastal," and to other parts of the world. Many of his travels were connected with particular opera performances; he saw many of his favorite operas dozens of times. Sonbert had a legendary address book, and in New York would schedule literally dozens of meetings with a variety of friends and acquaintances. He also had many lovers; among the best known was the choreographer Jerome Robbins.

Sonbert did have at least two brief teaching stints, at Bard College in the 1970s and at the School of the Art Institute of Chicago in the late 1980s. He thoroughly enjoyed both, and was deeply appreciated by many students. A few of Sonbert's admirers prefer his early films, for their wild youthful energy, but most critics acknowledge that the later films, with their complex montages, represent his finest work.

In the 1990s the Museum of Modern Art, New York, and the Cinémathèque Ontario presented complete retrospectives of his work together with other films he selected.

It is not known when Sonbert first learned he was HIV-positive, but changes in his habits in the late 1980s - he stopped smoking, and began working out regularly - suggest he may have had himself tested early. But he kept his status pretty much a secret to most, even as the effects of toxoplasmosis slurred his speech and affected his cognition, even as he was dying.

For over 15 years he lived with graphic designer and art historian Ray Larsen, who died in 1992. He did ask his friend and former student, the filmmaker Jeff Scher, to complete his final film, Whiplash, according to Sonbert's instructions. Warren died at his home in San Francisco. He is survived by his companion, photojournalist Ascension Serrano, of San Francisco; his father, Jack Sonbert, of San Diego; and two brothers. Whiplash received its world premiere at the New York Film Festival in 1997.