When did Zimbabwe start experiencing political violence?

Zimbabwe enjoyed relative peace for many years between the post-colonial transition from Rhodesia to its current iteration. Political violence started to become a serious problem, however, during the late 1990s when long-time dictator Robert Mugabe continued to obstruct efforts by opposition politicians to allow free and fair elections. Mugabe had succeeded in consolidating power following the 1979 transition to majority black rule, mainly through out-maneuvering and physically marginalizing his main opponent for political power, Joshua Nkomo (the two men had led competing factions of black militants fighting the legacy of British colonialism and minority white rule.) Most of the late 1980s and 1990s, then, were relatively peaceful. Mugabe had defeated his enemies and was imposing socialist political and economic systems on Zimbabwe. Political violence resurfaced, however, during the late 1990s when economic mismanagement precipitated riots and the emergence of an opposition political party, the Movement for Democratic Change, whose leader, Morgan Tsvangirai, a one-time Mugabe ally, sought to force democratic changes. Ultimately, Mugabe was able to repress the democratic movement and reestablish absolute power. Until, that it, very recently.
In the intervening years between the early-2000s, when Mugabe was repressing opposition political movements, and the present, when economic mismanagement continued to fuel social unrest, he repeatedly oversaw sham elections in which he was “reelected” president of Zimbabwe. Tsvangirai, however, continued to be a major player in the nation’s turbulent political scene, despite Mugabe’s repeated efforts at marginalizing and persecuting him.
As Mugabe grew older, his paranoia—the paranoia that tends to occupy the minds of increasingly isolated and autocratic rulers—intensified. The country’s economy continued to deteriorate, and hyper-inflation set in, with the consequent rise in political and social instability that eventually forced Mugabe from power. By late summer 2016, the situation became untenable. Public discord, including rioting, increased while Mugabe resisted calls for his resignation. Finally, in November 2017, the Zimbabwean military stepped in and forced Mugabe to resign and to vacate the presidential residency.
All this history is provided for the purpose of explaining why it is difficult to provide an exact date for when political violence began in Zimbabwe. Violence never really completely left post-independence Zimbabwe because of the dictatorial proclivities of Robert Mugabe. If one were to offer a possible answer, however, one could suggest that the violence during and following the thoroughly-corrupted elections of 2008 marked the beginning of the end, or, more recently, that the rioting that precipitated the November 2017 military take-over is the answer to the question. Over 20 years of political violence resulting from Mugabe’s inability to manage his country’s economy and marked ability at remaining in power provide multiple possible dates to the question when the violence began.