Are you drinking any energy drinks? Some make you shiver on purpose, the idea being that your body uses a lot of energy to shiver so it helps to burn calories. I know Redline from GNC does this.
Body temperature is controlled by your thyroid, which is controlled by your pituitary gland, which is controlled by your hypothalamus...it could be a problem somewhere along this line (and you haven't shown any other symptoms, yet), or it could be something as simple as a viral or bacterial infection.
You're sure there are NO other symptoms?...thinning hair? dry skin? losing weight? gaining weight? puffy eyelids? tremoring hands (even when you're not cold)?
How often does this happen? At a particular time during the day? Was it sudden onset, or has it been going on for awhile?
Feel better soon!
Are the symptoms of feeling cold and chills(shivering) accompanied by any fever?If yes,then it can be a bacterial or viral infection.
If there is no fever associated then it can be due to hypothyroidism,anxiety and panic atteacks,hypoglycemic attacks,hyperhydrosis(excessive sweating) and premenopause in women.Sometimes, patients who have recovered from a febrile illness continue to experience chills in the convalescence period.
It is advisable to first have the investigations for fever like ESR,complete blood count,blood culture,blood test for malarial parasite,widal test,x-ray chest or sonography to exclude any of the pathologies associated with fever.If negative,then other causes of shivering and feeling cold should be looked for.
Hope it helps.Take care and pls do keep me posted if you have any additional queries.