Train drivers, controllers and service employees organised under the GDL trade union of German railroad engineers and the German Civil Service Federation (DBB) walked off the job for the surprise strike as the early shift began.
They are hoping to pressure employers to increase salaries and provide better schedules, the DBB said.
The indefinite strike will cause delays and cancellations for tram, metro and bus service. S-Bahn commuter trains, run by national rail provider Deutsche Bahn, will not be affected.
The group staged its last strikes on September 10 and 15, but these didn't have a serious effect, according to broadcaster Bayerische Rundfunk.
Deputy leader of the DBB, Willi Russ, blamed the transportation firms for the latest strike.
“It was in their hands whether or not to prevent a strike during Oktoberfest in Munich,” he told news agency DAPD. “But they didn't use the opportunity. And our offer is still valid – as soon as the Bavarian community employers association signals its ready to talk, we're available.”
The union alleges that drivers have been poorly treated for years when it comes to scheduling, and have suffered more than other city transportation employees. Drivers end up working 42 to 43 hours per week to earn a salary that was agreed to at 38.5 hours per week, they say.
The strike could last through the weekend, Bayerische Rundfunk reported.