Any work done or changes made before this happened? What sort of ignition system does it have? It sounds as if you're losing electrical supply to the ignition system and the gauges. So check connections at the battery and the battery and engine earths and have a look at the ignition switch and its connections. Wiggle each while the engine is running and see if you can reproduce the problem. If you can't then inspect, wiggle, disconnect, clean, reconnect. Have you got a multimeter and would you like the wiring diagrams? Jonathan