The next morning, I inspected the hallway and discovered an old programmable thermostat I had almost forgotten about. Its settings showed that the heating system changed automatically during the night. I checked the schedule and found a temperature adjustment programmed for three o’clock. Suddenly, the mysterious clicking sound made sense.
Still, I wondered whether temperature changes alone explained everything. I began researching sleep patterns and learned that our bodies naturally move through different sleep stages. During lighter sleep, ordinary environmental changes can wake us more easily. But there was another habit I hadn’t considered.
