I have vibration when applying the brakes but... it doesn't happen that often. Seems like it will happen throughout the entire day one day but then a few days will go bye they work normally.

 

You've got a case of brake judder, it can have several root causes, here's a thread that's full of good info.

https://www.chevyhhr.net/forums/brakes-%7C-suspension-%7C-shocks-%7C-struts-24/brake-rotors-39572/

 

If this issue continues to be consistent I would advise that you take it into a dealership to be diagnosed. If you would like me to look at the history of your vehicle you can send me your name, address, vehicle identification number, and current mileage. This will allow me to do further research.

Jessica L.
Chevrolet Customer Care

 

I have had mine go away at different times by, rotating the tires, changing brake pads, changing brake rotors, changing hub/bearings, changing struts, adjusting the rear brakes and changing lower control arms. Each solution worked for a time.

The only things I have not done is tie rod ends, intermediate shaft and rack and pinion.

I think what you are describing is brake lining swelling, not to worry too much, they just sometimes get hotter or colder than they like to be. (like my wife?).