What country? This is different between different countries.
I can give the sequence in Poland, which is standard in most of EU.
- 180 seconds of Blinking Yellow. (Groups [**] with Yellow blink yellow, the rest remains off. If the controller was already in this mode, past duration is counted towards the 180 seconds.)
- All Yellow. Whichever groups don't have the yellow signal, display red.
- All Red. Duration of the shortest Intergreen[**] time, no less than 5 seconds.
- (optionally) - Startup program. A short custom sequence that opens most prioritized lanes (through normal sequence, like 1s of Red+Yellow, followed by Green).
- Standard traffic program. Normally side lanes are opened first, main direction later.
Ending just requires minimum intergreen of red signal after stopping all groups normally, before transition to YB - the controller can transition to dark (off) 180 seconds later.
[*] Group - a set of signal lights (often just one signal light) that display the same signal. May be a set of lanes that allow transition to the same exit, or a signal light hanging above the lane, repeated by another on the side of the lane - or two signal lights on two sides of the same zebra crossing.
[**] Intergreen time - time between stopping one group and activating another, necessary for vehicles/pedestrians to vacate the crossing without risk of collision with traffic from the newly opened lane. The intergreen times are assembled into a matrix, each starting group to each ending, with non-colliding entries empty, the remaining containing time that needs to count down from the end of the ending group) before the starting group is allowed to start.
Below is a standard stop and start sequence of a controller; diagram states of each group. The numbers above the diagram are the second of given phase, and phase number of given program. The names on the left are the group names. The program is made for development purposes, so it doesn't retain the 180 seconds restriction on yellow blinker (just to save the time of the developer); actual traffic program would require a 180 second gap between the start and end.