Vauxhall Zafira speedo intermittent/not working

Just recently,when I start the car for the first time, in morning or late afternoon after work, the speedo does not work and the engine cuts out as soon as I take my foot off the throttle. This happens maybe two to three times, then when I have been driving for 15 minutes or so the engine cutting out does not happen, but the speedo is somewhat errayic, sometimes works sometimes doesn't.
Not too bothered about the speedo, can judge speed from rev counter, its the cutting out.