Hard to step down brake pedal

I have Lexus ES 350 2010 and recently I found it is very hard to step down the brake pedal when I start the car with smart key after 5-day vacation back without drving.
I tried many times with smart key close to the start button, and then I can step down the brake and start the engine.

Could anyone tell me why this happened? It is a new car with 3000 miles only.

Thanks a lot.