Recently I noticed some unusual problem with brakes. When I lightly press brake pedal car slows down, but braking is not as linear as it used to be before. At first it slows only slightly, and if I increase pressure to the pedal it feels like stuck, but then it suddenly overcomes resistance and front wheels almost get locked. It does not happens all the time. And usually after strong breaking it returns to normal for a while. Did anyone have similar experience?

 

You're right to suspect a problem.
Braking should be smooth & linear with no bump in pedal feel.
It sounds like maybe a brake booster/servo problem.

Get that baby to the dealer or a brake shop.

 

dirty slave cylinder.