If you even have the littlest doubt that it is comming from the head or head gasket, I would stop driving it NOW. However, there are a few different possibilities. If you have an older E36, '92-'94 and you have recently removed the cap on your coolant resovior, the o-rings tend to go bad and the general sealing capabilitys of the cap are compromised, causing a leak of a rather horrible appearance. If you can narrow it down to this, I would get it fixed as soon as possible, but just watch your coolant level and your temp and you should be fine. Pretty much the same story with the hoses, but again, get them fixed as soon as possible. While you are terring down your cooling system, you might want to check out your water pump and see if it has plastic or metal fins. After a while the plasic ones wil decompose or something, break apart and get sucked into the cooling chanels in your head. That would quicly turn into a $3000 water pump/head job, its better to check it now. But if you see it weeping from around the bottom of the head or is you can blatantly see a crack in eaither the head, or head gasket, I would park it and have it towed to your favorite BMW shop.