My ABS light sometimes comes on when I start. However the next day it doesn't, then maybe a day or two later does it again. This was happening before I had the front discs and pads replaced last week as they needed doing anyway, and the light stayed off for a couple of days and then came back on today when I restarted it after going to a shop. The brakes feel normal - any ideas why it should be intermittent instead of either on or off?

 

Have you checked the fluid level underneath the hood?

 

Just checked it and it was at the right level.

 

The most common problem of ABS system is broken sensor wire. Visually inspect wires (turn wheels right then left)
If you don't see anything, go to repair shop to read ABS codes, some cars blink codes.