Commuters on several subway lines experienced a stressful start to their workweek on Monday as trains faced significant delays due to signal, switch and mechanical problems, the MTA said.

MTA officials said a signal problem at Nassau Avenue led to a complete suspension of G train service between Court Square and Bedford-Nostrand Avenues in both directions just after 8 a.m.

By Monday afternoon, the MTA said G‌ train service had resumed between ‌the two stations.

Some southbound F trains were temporarily rerouted to the G line from Queens Plaza to Bergen Street to provide limited southbound G train service.

Meanwhile, on the R line, straphangers temporarily grappled with extensive delays in both directions due to a switch problem at Queens Plaza, according to the MTA.

And just before 9 a.m., officials said that Eighth Avenue-bound L trains were running with delays after a train with mechanical problems was removed from service at Atlantic Avenue. By Monday afternoon, there were no service alerts along the L line.

Riders waiting for 57th Street-bound M trains Monday morning also faced delays as crews worked to determine why a train's brakes were activated after leaving Central Avenue in Bushwick, the MTA said.