Neff B1422 oven - thermostat light?

When switching oven on using circotherm the thermostat red light appears and then switches off once it has reach desired temperature. However within minutes of this the red light re-appears and then goes through on and off throughout the cooking time. Is this normal? My interpretation of the user guide suggests the light should stay off once the desired temp has been reached. The air blowing out of the top of the oven is continuous too (cold at first and hot thereafter).