Had this problem - is this in relation to the bumper accident?
This is a typical problem with the e36's as far as I know. The problem usually is a leak from the transmission radiator in the front just behind the two grilles; a stone chip or minor dent can cause a relatively insignificant leak; but this is a transmission radiator, so this has the potential to be a very expensive fix if not done soon.
The trans radiator itself is 80-100 dollars depending on who you're getting it from (any more and you're being ripped off). Forking over another $50-100 for installation/replacement would be normal, unless you plan on doing it yourself. If this is the case, you should also get your transmission flushed - might as well.
To see if this may be the problem, lay some paper towels under your car overnight, just underneath the center of the front bumper. If you see pinkish splotches the next morning, get that fixed!
1998 BMW e36 M3 Sedan
Crap, I think I may be a yuppie...
2003 MINI Cooper