I had a strangely similar incident on my 85 380se. Turned out to be the linkage getting stuck on the spark plug wire harness. All was fine until the accelarator was pressed more than about half way. If i got on the pedal too hard it would stick and I also had to lift the pedal with my foot! Did the exact same thing with the cruise. Only when I hit resume after slowing quite a bit. These cars accelerate pretty hard to get back up to speed so I imagine the pedal goes quite low. I tied the harness away from the linkage with a wire tie and it never happened again. Worth a try!

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U. S. Air Force Air Traffic Controller
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