Hey mate.
Shuddering when braking can be a large number of things.
Does it shudder when taking off (more so when fast) as well?
A few things that i know can cause it, if its shuddering on light braking, id suggest it could be warped rotors, possibly get these checked, if it is then have your rotors skimmed and get new pads.
Unless your rotors are just slightly warped, you may be able to feel your brake pedal pulsating whilst its shuddering, this is a pretty clear indication that thats the problem.
Also try replacing your spark plugs, leads and coils. I had a big problem with shuddering during take offs and replacing these things fixed it up perfectly.
Getting these things looked at/replaced is probably the first thing id do as its my understanding that they're the more common causes when dealing with shuddering during taking off and braking.
If its making a 'grumbling' kind of sound, then it could possibly be your wheel bearings as well, but that would be the case if the wheels were shuddering pretty much all the time.
If you are feeling the shudder more in the steering wheel, my suggestion is that its something to do with the front calipers/rotors/bearings, or if its mainly in the pedals then id be looking at the rear.
Can be a pain trying to eliminate the problem but id say take it to a mechanics with these things in mind and a few hundred dollars later you should be smiling.
Hope this helps bud.