Welcome erin8817,
You own a pre-register 323i right? ^_^
Just go and study your owner's manual,
If I am not mistaken, BMW recomended for 2000 km break in period and during this period the car speed shouldn't exceed 150 km/h.
Surprisingly is BMW don't belive in standstill warm up, they suggest that after starting the engine drive off straight away with low speed and the machine will reach the working temparature later.
Enjoy your ride, Cheers.