Gorgeous car you have there. For a good starting place to assign a avalue, try NADA.com, specifically
1958 Mercedes-Benz 220S 4 Door Sedan Prices, Values & Specs | NADAguides
Kelly Blue Book won't go back that far.
Note that you might not get what you want, regardless of what you want out of it - this isn't the best market to sell a car right now. I recently sold a car for about $3000 less than its worth because of the market.
That stated, and I'm not trying to posture shamelessly, I'd be interested in knowing your price. I've got a 108 and would like a reason to sell it off

Yours is as good a reason as any. Do you have a clear title to it?