1993 Lexus SC 400

Strange problem w/93 Lexus SC400, it has 200K miles and when you start driving the car if you let off the gas it starts making a grinding noise and when you put on brakes the grinding gets louder, car shakes, dash lights flicker and A/C doesn’t cool. Once the car is driven for 10-15 minutes there isn’t any more noise, no shaking, slight flickering when braking and A/C gets very cool. We have replaced alternator twice but the flickering dash when braking persists. The car is great otherwise but seems to have some electrical issue going on. Based on all of the miles we don’t want to spend too much on it. Any ideas??

It looks like two problems: grinding brakes, and an intermittent open in electrical.
The grinding brake may be a worn-out brake pad, or, the brake pad backing rubbing against something.
To hunt for the wiring problem, turn the ignition switch ON. One person watches the dash lights, while the other person gets under the dash and moves, and wriggles, every wire under there. If/when the dash lights flicker, keeps wriggling wires until you have located the particular wire causing the flicker. Then, repair that circuit/wire.