If you mean that the brake pedal starts sinking to the floor after these stop and goes, the problem might be with brake master cylinder.
The brake master cylinder resides under the hood. And engine heat under the hood can cause the brake master cylinder to start leaking internally. The brakes fade when things get hot. Let things cool down, and the brakes work again.
Tester
Just has hot brake smell,tiny drops of what I presumed was brake fluid under car,pedal and brakes seem to work fine
Thanks to all for help,Jeep mechanic replaced 02 sensor,Jeep runs great,no more smells or problems though check engine light is still on.
If your check engine light is still on, you are just whistling in the dark and pretending all is well.
At least the thing is running well,I can continue working,not kidding when I said I had hoped someone had a āthat happened to me and all it is isā answer,I was told it had other sensor issues to do with emissions,I wonāt get into how I feel about VT emission laws!!