Microwave works few seconds, then stops

Microwave works a few seconds, then stops and 88:88 appears on screen. After about 5 seconds screen goes to ‘0’ and clock time has disappeared. When reset the unit will operate for a few seconds but usually stops again after 1 to 15 seconds. Have unplugged and replugged unit with similar results. When I hold my finger on the start button the unit will run for a few seconds and stop with the error code --SE-- appearing.