Change your bellts and oil. By this moment there should have been at least 12 oil changes (i dont think anyone has done it thoug). Use only high quality oils such as synth. Castrol, etc. Besides if thats an auto-change your tranny oil. If you will keep it for a while get some Bimmer fuel addities to clean up the fuel system, etc. (they do work in the long run). Then replace the fuel filter and maybe the plugs. If you do a nice complete tune up on this car prepare to spend a lot especially at the dealer.