You may have a vacuum leak.

Remove air filter box and spray some plastic/rubber friendly fluid like electronics contact cleaner that will disapate quickly around the injectors, and vacuum hoses.

If no vacuum leak, check the Idle Control Valve, remove for cleaning using a Carb Cleaner spray until it come out clean, rattle it couple of times during the process and then finish with a bit of silicon based lube, re-attach. It might also help to check the ohms on it to insure it is within tolerance.

But I default to a vacuum leak.

Personally I found a huge leak on injector #4, She also started right up, did the warm up stage then when she drop she felt she would die. I popped the idle control breather and she immediately died.

Jim

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05 CLK320 Cabrio
85 911 Carrera Targa
96 Lexus ES300