When you say your fan is spinning how fast is it going? The reason I ask is that clutch fans are designed to free spin all the time and as the air flow gets hotter the clutch engages gradually until it is fully engaged when the designated temperature is reached. I don't think you have a problem.
You should see a visible difference in the speed of your fan when the car is hot as opposed to when you first start it in the morning.
88 230E (W124)
[This message has been edited by yal (edited 08-29-2000).]