Loss of All power, car stalls.

2001 Daewoo, New Battery, new sensors. Power shuts off. Radio, lights, everything. Starts again after a while.
No warning, At red light. While moving. Just dies. It runs well outside of this. Oil leak. Oil level fine. Coolant fine. Just changed front tire arms and rack in pinion. Trans fluid. Any suggestions? Shutting off is dangerous, don't want to go car shopping, not yet. Help for my mechanic? He says Daewoo with out engine code is hard to fix. I also cant afford to have him 'guess'. Thanks