My 88 Ramcharger also does this. Its usually just the first time, or two, that the brakes are hyper touchy, then good.
Its done it on two different sets of calipers, rotors, and master/booster setups, so I have no idea. I just live with it for now. I can never duplicate it for a mechanic, everything has been inspected and seems to be working within parameters.
Fits my problem to a T and I also went thru what you did and been living with this also.
This is from a Jeep forum and has to do with drum brakes:
The OP wrote:
Anybody else have this problem, when I start the Jeep up in the morning, the brakes are crazy sensitive, like I tap them and its like I slamming them on.. but once the car warms up or is driven a bit they are normal.. this normal, or something I should care about, its more of a nusiance when I almost knock my head off the steering wheel every morning when I stop for the first time.. 
Then further on he wrote this:
It is caused by a thin film of rust inside the drum brakes. It is not just Jeeps that this happens to, but potentially any vehicle. I had a Lumina van that would lock up so hard that the ABS would kick in! After a mile or so, the rust is worn off and the brakes are back to normal.
And this after many challenged or question his diagnosis:
yeah...seems crazy... But it is the coefficient of friction that changes. For example, if the coefficient of friction for your brake shoes is 2, that means that for every pound of force applied to each square inch of brake shoe, the effect of the friction will be 2 lbs of force against the "sliding" surface of the brake drum. With a thin film of rust, which can easily slip in between the drum and shoe, the cf may increase, let say to 10. Now when you gently feather the brake pedal and apply that same 1lb of force, there will be 10 pounds (instead of 2) of force at the "sliding" surface of the brake drum. Hence the extra braking power!!
Don't shoot the messenger, just what I found on the internet so it must be true or so
Now you'll come back and say your D250 has four wheel discs and I'll be
and you can
me
