The driveshaft center bearing, and support could be the cause.. Apparently a fairly common failure at over 100K miles..
I posted a "how to" article on replacing them a while back on a 300sel..

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89 300SEL Money Pit

92 Blown Buick Ultra Pimpmobile 220K and adding 1K per week

88 Wagoneer Slightly modified (Not for soccer moms)

04 Kia Sedona with every option... NICE