My basal body temperature is within the range of 35.8 to 36.1 during non-ovulation period. How could it be so low? How to increase body temperature?

That's a bit low. so if measured correctly, you should probably have your thyroid hormone levels (T4, T3, and TSH) checked to see if your thyroid is underactive.
It depends on how. you measured your basal body temperature. But assuming it was either by ear or rectal, I would consider seeing a healthcare professional to confirm your measurements then help you figure out why your core body temperature is low. It is not always easy to find answer for, but it is generally fun for the healthcare professional to do especially if he/she is thorough.