If you search on "C230 seat relay" then the first thread in the list of results is this one:

http://www.peachparts.com/shopforum/showthread.php?t=132934

This will give all the info for the problem I know about. Not sure if it is what is ailing your car but the symptoms seem the same.

Mike

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra