Calls every few days and never leaves a message so it's likely a scam.

Says I have a civil suit in Polk County

Calls every other day. Leaves no message.

This is a fraudulent call. It is an organized crime syndicate. They call claiming to have "certified legal documents" they need to deliver regarding a court case. They are soliciting "payment information" in order to serve these documents. Failure to pay the fee they threaten will result in police delivering the documents along with an arrest. Court summons and legal notice do not require a payment / fee to be paid by the recipient, and they are never "scheduled." The group operates fly-by-night "collections" call centers around the country hiring people who honestly believe they're working for a "real" collection agency. The FTC and law enforcement keeps shutting them down, but they just keep reopening new shops in cities across the country.

Wow....for being a Prosecutor you sure don't know how to spell your job title.