Brief Answer:
Possible causes are given.

Detailed Answer:
Hello,
Thanks for the query.
The most common cause for chills without fever is exposure to cold, where the body try to produce heat by chills and sweating is the end result.
Underlying chronic infection like urinary tract infection is another possibility. Hypothyroidism is another rare possibility.
As a first line management you can take over the counter available paracetamol tablets for symptomatic relief.
If symptoms persists basic evaluation has to be done to look for underlying causes, which includes complete blood count, urine routine, and a thyroid function test(TFT).
Hope I have answered your query.
Thanks

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