Barth was born in Herold. He began his career as a DKW motorcycle racer and later switched to BMW sportscars. The East German factory of BMW would become the Eisenacher Motorenwerk (EMW) after the war, driving the factory team car in the East German Formula 2 Championship, which he won in both 1952 and 1953. He was allowed to participate in three events in the West in 1953, including his first appearance in the Formula One World Championship. He finished fifth in the non-championship Eifelrennen, but retired from the Avusrennen and the German Grand Prix.