Hi! My wife has a '99 SC2 that randomly dies and will not restart. When
it chooses to stall everything shuts down including the radio. You can
turn the key to engage the starter but nothing happens. It doesn't
matter if it's highway or city driving. It just dies. Then suddently
after a few minutes, you can turn the key and it will start up like
nothing is wrong. It is a problem that comes and goes with frequency
and has been getting worse lately. Today she was left stranded in the
middle of a busy intersection. I'm am guessing that it's the main relay</span>
or Ignition Module but I'm not sure where it's located on this vehicle.
I don't have anything to scan the ECU for CEL codes and I guess her car
doesn't have a Self Diagnostics since it's OBDII. Does anyone have
suggestions or had the same problem happen to them?

Okay, since no one can help me there, Does anyone have an Electrical
Schematic of the '99 SC2? Also, where is the location of the main relay?

lots of problems with the negative terminal on the battery. bat terminal cracks inside the battery causing the exact problem you are having. pull of the negative treminal and check for any corrosion or clear fluid(battery acid) if so replace the bat and the terminal end of the cable. Just about all saturn shops keep these ends in stock cuz we replace so many of them. keep me posted.