You are going to have to get some scan codes. I can't tell where you are, but you might be able to go to a local parts store and have them run a scanner on your car. It's called an OBD-II scan and the scan port for your car is under the dash near the steering wheel, probably behind a little door under the dash. The codes wil tell you what kind of problems you have. Without that, everyone is guessing.
Hope that helps.
Current cars: '99 E39 wagon (200k+), '99 E36 Cabriolet (220k+), GMC Yukon Denali (186k+, but who cares?)
Prior BMWs: '99 E39 (120k), '94 E34 (220k), '93 E34 Touring (320k), '86 E30 (275k), 76 E12 (175k), '74 E10/model 115 (2002 tii) (110k)
BMW's run forever and the Internet is a nearly infinite resource. Use them both wisely for maximum enjoyment and return on your hard-earned cash.