expression, godan verb (-ru)
get into a specific mood; switch on (figuratively)
Idiomatic expression meaning to suddenly enter a focused, motivated, or characteristic state, as if a switch has been flipped. Often used for work, performance, or personality shifts.
彼は試合になるとスイッチが入る。
He switches on when it's game time.
It takes time for my work switch to flip on.