Why does the car pulsate when braking at higher speeds. Car shakes

What is your question?

When driving at higher speed, when braking car pulsates and shakes. I had the brakes done 4 months ago, so thought that was the issue as it did this when I needed brakes. Repair shop said brakes are fine.

What makes this problem better or worse?

Brake take foot off brake, brake again, repeat

How long has your 2010 INFINITI EX35 had this problem?

A few weeks