The Covid-19 pandemic abruptly disrupted the lives of millions, leading to a profound and radical transformation in daily routines and lifestyles. This unprecedented situation influenced spontaneous cognition, particularly involuntary mental time travel—the involuntary retrieval of autobiographical memories or the spontaneous imagination of future events. In this chapter, we first present three studies that explored involuntary mental time travel during the Covid-19 pandemic, examining its relationship with the pandemic context, lockdown conditions, and individual mental health. We then discuss the underlying mechanisms that may explain the observed increase in involuntary autobiographical memories and future thoughts during the Covid-19 pandemic, including changes in the availability of attentional resources, changes in life circumstances, and growing personal concerns. Finally, we examine the relationship between the increase in involuntary autobiographical memories and future thoughts—sometimes described as intrusive—and poorer mental health in individuals, highlighting potential traumatic stress reactions triggered by the Covid-19 crisis.