What Causes Recurring Low Grade Fever With Muscular Fatigue?

I have had some consistent low body temperatures throughout the past month, A couple times a week at least I experience muscle soreness especially in the legs, my feet get very cold and I have the actual shivers for about 10 to 15 minutes with no accompany fever ever. some general fatique, some difficult with sleeping waking up every 2 to 3 hours. No other accompanying flu symtoms. 65 years old, and when looking up in the merck manual have a similiar presentation of hypothyroidism. Wondering about getting a TSH thyroid level?r