If you missed your court date for a criminal charge, a warrant may have been issued for your arrest. Normally, notice of this type of warrant gets mailed to your last known address. You can call the Polk County Clerk of Court to check about this type of warrant at (515) 286-3765.
If you think there is a warrant for your arrest because of a new criminal charge, you should contact your local police department to turn yourself in, if such a warrant does exist. Warrants for new charges are, by law, confidential and not disclosed by the Clerk of Court because some people wanted for a crime would flee the jurisdiction.