Speedometer inconsistent

For my Punto Diesel the speedometer is behaving inconsistent. All other reading on dashboards are working fine as per observation. Sometimes it works normal and sometimes the needle is dead. Battery is new, car is recently serviced. No error indications on dashboards. OBD scan shoes error related to Lambda sensor but no check engine light. Most of the time speedometer start behaving normal after covering a distance. What should be checked ?