Having to top oil on my vectra 2004 model sl often

[iyke]

I have noticed that my car has been shorting oil quite often i have checked for any sign of leakage but there is none could anything be wrong with my engine ?
Secondly in the past two week i have experienced strange behaviour from the car it will start but refuse to move when engaged in gear with engine vibrating when we called the AA and waited for them to com the car starts to work fine. this happened two times in a week could any one tell me what could be wrong with my car?

[m8internet]

Could you please advise as to what engine it has
How long / many miles since last service?
Have you tested for clutch slip?
What condition is the oil in?