Hello,

I also suspect electrical problem.

Check the ignition amplifier aka power module in the engine bay. If its heat grease had flaked & dried then it's time for a fresh one.

Check also the radio suppression relay. Ensure its electrical contacts are clean. I don't know how to test the relay. The next time it happens immediately wire a jumper between the grey and red wires in the relay socket. If the problem clears immediately then it could be the relay.

Fuel pump relay could get very hot as it is actually two relays in one casing. You can drill holes thru its casing to air cool it down. Don't replace it yet. Maybe it could help in your situation. If you're up to it you may direct some of the cool ac air from its pipings behind the relay cluster board. These are mentioned in the FAQ.

Hope these helps,
Amarin.