Diagnosing over the web is a shot in the dark. My '91 300-SEL did the stalling bit some years back. Did not experience the shaking.

Replaced the OVP - over voltage protection relay. It's in the firewall area midway across. You can look up a photo at this sites parts section. An easy DIY replacement.

I would first look for disconnected/leaking vacuum hoses.

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Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"