Does it sound like scrunching up piece of crinkly paper? If so, it could be "crepitus" (a particularly useless term when you read its definition: "A clinical sign in medicine characterized by a peculiar crackling, crinkly, or grating feeling or sound under the skin, around the lungs, or in the joints").
As you can see from the definition, it's a joint (not muscle) issue.
Typically, if it doesn't hurt, you live with it and move on. If it starts to hurt, go see your Doctor - there are some things they can do to help (but not cure - to the best of my knowledge (and I have searched), there is no "cure").
Crepitus is relatively common in knees (I have a scrunchy right knee - no pain). Here's an informative web site on the subject, albeit knee-related:
Also, type Crepitus in your search engine and have at-it.
Regards and Happy New Year.