Aside from the minor vibration i get when the brake is applied during highway speed, i recently noticed this problem:

My car has around 5000 km, but whenever i applied the brake (at idle or crawling spped), i hear a 'psssst' sound, similar to air/gas leaking. My first thought was my brake line had air in the system, and i need to bleed the brake fluids. But since my car is still relatively new, could such problem occur?? I never heard on anyone bleeding their system at such early stage.