As has been frequently the case, it could all start by a local clash in some provincial town or village over mundane things. Local security apparatus, whose effectiveness has been eroded steadily, fail to put down the unrest, and it lingers on. Copy-cat unrest start to happen. Again efforts to put them down is inept and poorly coordinated. People sense that the authorities are now just a paper tiger. This would send shock wave to Pyongyang, where some faction, which kept its head down despite it being marginalized for some time, finally decided to move against the leadership.
It is one of the ways things can unfold.
I really doubt it will start in Pyongyang, but will go from the roots of the tree to finally infest the trunk of the tree, in this case. Too bad we dont have a Reagan in the White House, because the heroic North Korean people could depend on the US to back them up in such a situation, through a variety of measures. Can’t count on it with Obama and how he left the Iranian people out to twist in the wind.