ABS light is on frequently
 

My Camry 02 ABS light is on. When I start the car it goes on for a second then goes off. Few minutes after I drive the car in the morning it comes on. If I drive the car in the lunch time or on the way back home the ABS light stay off.
I checked the air pressure on all tires and they are all equal. Any idea for what to check? Thank you.

When the the light is on have someone read the troublecode(s) from the ABS computer.

I have not read the error code but will try to do it this weekend.

its probably a wheel speed sensor starting to act up.

There is no error code from the hand tool.
The light started to come out all the time once the car starts moving.
Any idea how to troubleshoot this ABS light? or instruction to how to check the wheel speed sensor? Thanks