Born in Orselina, Switzerland, on 7 December 1917, Volonterio came from Swiss noble stock and pursued a legal education before directing his energies toward motorsport. His entry into racing came through sports car events, which at the time offered privately funded Swiss enthusiasts a natural pathway into European competition. Switzerland's long tradition of affluent gentleman racers made the transition from professional life to the cockpit a well-trodden route, and Volonterio followed it with sustained commitment.
Volonterio made his Formula One World Championship debut at the 1954 Spanish Grand Prix, held at the Pedralbes street circuit in Barcelona. He shared a Maserati 250F with his compatriot Emmanuel de Graffenried, but the pairing was forced to retire when the engine failed and the car could not be classified.
He returned to championship racing two years later at the 1956 German Grand Prix on the Nürburgring Nordschleife. The brutal fourteen-kilometre circuit demanded enormous stamina and precision from all competitors. Volonterio completed the race but finished six laps behind the winner Juan Manuel Fangio and was not classified in the official results. The enormous lap differentials common at the Nordschleife in that era reflected the gulf in resources and machinery between leading works teams and private entrants rather than any failure of resolve on the part of the backmarkers.
His third and final World Championship appearance came at the 1957 Italian Grand Prix at Monza, where he shared the car with André Simon. The pair finished eleventh overall, fifteen laps behind the winner Stirling Moss. Completing the distance at Monza, one of the fastest and most demanding circuits of the period, represented a creditable performance for a privately entered machine.
Beyond his three championship starts, Volonterio remained active in the wider non-championship Formula One calendar, which in the 1950s still included numerous prestigious races of significant prestige and prize money. His strongest individual result in this sphere was a second place in the Coupe de Paris at Montlhéry in 1955, a commendable finish at the historic banked oval circuit situated south of Paris.
Volonterio also extended his involvement in the sport by fielding Grand Prix cars as an entrant for other drivers. This dual role — active competitor and team owner — was characteristic of the privateer culture that sustained Formula One's grid depth in the pre-commercial era of the championship.
Sports car racing ran as a consistent parallel thread throughout Volonterio's motorsport career, from his earliest competition years through to his final seasons. He continued to race actively until 1973, a span of roughly two decades in the cockpit that demonstrated deep personal commitment to the sport well beyond any ambition for championship glory. His longevity in competition set him apart from many Formula One entrants who restricted themselves to the brief peak of their Grand Prix careers.
Volonterio died in Lugano on 10 March 2003 at the age of 85. His career traced the arc of the classic 1950s gentleman driver: a man of independent means and professional distinction outside racing who competed at the highest level available to a private entrant, contributed to grid numbers at a time when the sport needed them, and kept faith with motorsport long after the championship headlines had moved on to other names.