Hello I will help you with your question,
Is this motion at slow speeds or all the time?
What condition are the tires and wheels?
motion in slow to medium speeds then shakes the car on the highway
tires are not in bad shape
just had front new brakes also put on about a month ago but now thinking of it when my girlfriend drove the car today you could smell the front brakes burning a little bit
This sounds like one or more tires has a seperated belt causing it to bump as it turns.
What did the shop say when they changed the brakes? Did you ask about the vibration?
vibration was not there jst started happening
If this just started have someone walk wlongside as you drive very slowly in a parking lot to see if the wheels/tires seem to rotate smoothly. It does sound like a tire is damaged, a wheel is bent or loose and that is what you are feeling. You should be able to see this as it turns.
You can use your hands to run around the surface of the tires to feel for lumps but be careful and wear gloves as you can be easily cut if there is a piece of glass or wire in the tread.
Let me know what you find and we can work from there if necessary