ABS and STC lights illuminate after about 30 minutes of driving. Disppear again. on 2000 Volvo C70

The ABS and Stability traction control disengaged light illuminate after about 5-30 minutes of driving. But turn off and are not on when I turn off and restart the engine only to
randomly reappear. I just had major service performed at 75,000 miles and replaced battery, oxygen sensor, ignition coils, etc. The computer did not find anything wrong with the brake system nor did the mechanics.

Asked by for the 2000 Volvo C70
scan abs codes and post so we can adv