Good day. Baby is 9 months old. Since birth, the baby has slept throug…

Good day. Baby is 9 months old. Since birth, the baby has slept through the night without waking up. Only during crises could the baby wake up a couple of times at night. At 6 months, the doctor prescribed us to give vitamin D three drops per day for a month and then two drops per day. And since 7 months, the baby started waking up at night, at least twice. Now he wakes up almost every hour. Could frequent nighttime awakenings indicate any kind of disease? Is this due to vitamin D? Two teeth have erupted, others are not visible yet but saliva flows. With the daily schedule all in order, I don't overwork or overstimulate. He sleeps 2-3 times