Sleeping poorly is a problem. Taking Prednisone won't help your circadian rhythm. For PMR symptoms to increase with more overnight inactivity is typical I would think. Since your sleep issues existed before PMR and Prednisone it is possible that your sleep / wake cycle was already dysfunctional and probably is a separate problem.

PMR symptoms of pain and stiffness are well known to be worse in the morning or after periods of inactivity. My pain and stiffness was so severe it woke me up in the early hours of the morning usually at 3 a.m. What worked for me was to take a small portion of my daily dose of Prednisone in the evening before going to bed. I was able to sleep the entire night without any pain. Getting a full 8 hours of uninterrupted sleep was good for me. I had a great day when I took the rest of my daily Prednisone dose in the morning when I woke up.

The combination of pre-existing sleep issues, the disruptive effects of prednisone, and PMR pain creates a complicated problem. I think we need more information.