Back pain/cramp since last 2/2. 5 years.

I have been experiencing a peculiar lower back pain/cramping issue for the last 2–2.5 years. During the day, I do not have any pain, stiffness, or discomfort, despite having a desk-based job. However, at night, after falling asleep around 10:00–10:15 PM and getting approximately 5–6 hours of deep sleep, I wake up with a severe cramp-like pain in my lower back. When the pain occurs, it becomes difficult to turn from one side to another while lying in bed. I usually have to sit upright on the bed, and after about 15–20 minutes, the pain gradually subsides and I feel normal again. This episode occurs almost every night and has been continuing for more than two years. I consulted a doctor at AIG Hospitals, Gachibowli, who suggested that it might be related to Vitamin D deficiency. My Vitamin D levels have since improved, but the nighttime lower back cramping continues without any significant change. I would like to know the possible cause of this persistent nighttime lower back pain.