Oil lights

Hi to everybody,

I have a Volvo 740 2.0 GLTs 16V and sometimes happens that I start and he/she remains turned on the spy of the oil and the motor it makes noise, then I turn off and turn on and everything is ok. What can he be? the pomp of the oil? Oil and filter have 6.000km and it are Mobil1...

Thanks!

-- Asterix (Bruno), Volvo 740 GLT 16V (21, 140, MI)