Unfortunately with that description almost anything could be wrong with your car. I would start by checking the vacuum hoses for leaks, then as has been said move onto the ignition/spark system. If those both check out move onto the fuel system. These 3 could be the culprits. The vacuum is easiest to troubleshoot and the fuel is the hardest.
I had a similar problem with my last 318 and it turned out to be the #4 injector which was shitting the bed and dumping way too much fuel into the cylinder.