According to the Science Daily article Plate Tectonics May Grind To A Halt, Then Start Again (Carnegie Institution), one main aspect of the research being presented is the hypothesis that
suggests that plate tectonics may have ground to a halt at least once in our planet's history -- and may do so again
Specifically, the article states that geochemical evidence of igneous rocks from about a billion years ago suggests there was a lull in subduction processes, coinciding with evidence of the closing of a Pacific-like basin, forming the supercontinent Rodinia. The lulls also, according to the article's authors, in part explain that
By periodically clamping the lid on heat flow, intermittent plate tectonics may explain why the Earth has lost heat slower than current models predict. And the buildup of heat beneath stagnant plates may explain the occurrence of certain igneous rocks in the middle of continents away from their normal locations in subduction zones.
However, the article rather vaguely states that
Rodinia eventually split apart when subduction and plate tectonics resumed.
What geological mechanism would cause a 'restart' of plate tectonics, specifically subduction?