Were your thyroid function tests done?
Are you on any medications?
Two of the commonest causes of chills without fever are abnormal thyroid functions and medications. I am sending you a link where you can read all other common causes for this like anemia, hypoglycemia, uncontrolled blood sugar etc. We physician if are unable to find anything wrong anywhere than would blame your diabetes and medications for it. You can visit this link:
Usually the approach for this is to get serial blood tests, chest x-ray and sonography done at 2-3 moths interval. Sometimes, initially all the things are normal but later on a small abnormality may be detected by these regular investigation. This clue can then be further investigated.
I don't know how much this has helped. If not, I would opt out and let my fellow experts take over.