Why Do Moments of Mindlessness Occur?

I noticed that at key moments, such as when I am using social media in a passive way, or when I am between tasks in daily life, I tend to enter a kind of 'habitual' mode of being. On social media I click aimlessly around, almost compulsively. In my house, I just walk around without much planning or purpose. **What could cause such mindless behaviour?** I am also wondering whether *merely* paying close attention to lapses in attentiveness and to distracted moments can ultimately lead to the elimination of such habitual behaviours.