A prisoner in custody under sentence and claiming a right to be released on the ground that there was such a denial or infringement of the rights of the prisoner as to render the judgment void or voidable under the Constitution of this state or the Constitution of the United States, may file a verified motion at any time in the court which imposed such sentence, stating the grounds relied upon, and asking the court to vacate or set aside the sentence. Unless the motion and the files and records of the case show to the satisfaction of the court that the prisoner is entitled to no relief, the court shall cause notice thereof to be served on the county attorney, grant a prompt hearing thereon, determine the issues and make findings of fact and conclusions of law with respect thereto. If the court finds that there was such a denial or infringement of the rights of the prisoner as to render the judgment void or voidable under the Constitution of this state or the Constitution of the United States, the court shall vacate and set aside the judgment and shall discharge the prisoner or resentence him or grant a new trial as may appear appropriate. Proceedings under the provisions of sections 29-3001 to 29-3004 shall be civil in nature. Costs shall be taxed as in habeas corpus cases. A court may entertain and determine such motion without requiring the production of the prisoner, whether or not a hearing is held. Testimony of the prisoner or other witnesses may be offered by deposition. The court need not entertain a second motion or successive motions for similar relief on behalf of the same prisoner.