Hindrances in Meditation: Sloth and Torpor (part 4, English)
It feels nice and cosy and you feel just a hint of drowsiness.
Two seconds later, you are nodding off. Which was not your intention.
I have actually seen (i.e. heard) people falling off their meditation cushion. And showing off their bruises on their forehead.
Here a short video on how to avoid bruises on your forehead. 😉