Oil lights

[Asterix]

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!