2002 buck Century, 137,000 miles

I have a 2002 century with grinding noise when applying brakes, and the low trac light will blink. Then after a few times the antilock brake light, thes ervice vehcile soon light and trac off light comes on, is this a major problem. When I have my husband check it it doesn't happen. Also when I turn the car off and back on, the abs lite and trac off light and service vehicle soon light is off.