Car won't start
 

This morning my car decided not to start.

It's an 09 IS250 with 55k miles. I've owned it for 4k miles and no issues so far until this.

I pushed in the brake pedal and hit start, and it made sort of half-start sound like it was about to turn on then it stopped.

After that, the brake pedal has remained pressed in and if I push the start button the electronics start but the engine makes a fast clicking noise.

Any idea what this is or what I should do?

Sounds like a dead battery. Connect it to another vehicle with jumper cables and see if it starts.

get a new battery