Infection with the Lyme bacteria can cause this sort of internal vibration - a type of paresthesia (peripheral nerve sensation). When it's mild, you may first notice it at night when your body is quiet and still.
The supporting cast features James Caan as the young gambler, Charlene Holt, Ed Asner, Paul Fix, Arthur Hunnicutt, Michele Carey, and Christopher George. El Dorado was filmed on location in Tucson, Arizona and Kanab, Utah, and was shot in Technicolor. The paintings in the credits are by Olaf Wieghorst, who plays Swede Larsen in the film. The musical score was composed by Nelson Riddle.
El Dorado County in Northern California. El Dorado County is located about 125 miles northeast of San Francisco The eastern county line of El Dorado County is located right in the bend of California's eastern state line. The El Dorado western county line is 30 miles east of Sacramento which is California's State Capitol.