Recently recovered from diverticulitis 2 weeks ago but since getting it 5 weeks ago everyday starting at 12pm i start running an elev temp of 99-99.8 until about 8:30pm then it goes back to normal without any fever reducers. what could cause this?

This might not be abnormal. Perhaps you don't have much previous experience measuring your temperature several times a day, but it is normal to have temperatures in this range in the afternoon and evening. 98.6F is not the top of the normal range, but the average over a day. Everyone's temperature tends to be higher in the afternoon and evening. But check with your doctor if you remain uncertain.

There is variation of temperature based on the hypothalamus and variation of chemicals in the body on a daily basis and that is what you are probably seeing and not necessarily a pathology. You do not have fever, and even fever has a purpose in homeostasis in the body.