1999 Cadillac Deville ABS and traction control

Often when I put on breaks, my break pushes back and I hear a click sound. My breaks seem ok. In the past, this happened only occassionally when it was wet/slick outside. Now, even on a dry day it comes on often. It goes off when the car is turned off and when it started back up, eventually it will come on again. I've been reading the comments and I'm thinking it may be the wheel sensors or maybe the lines need to be bled. I just had my rear breaks and drums changed.