ABS light comes ON

[DGomes]

Hello my friends hope you are all well.

I would like to share with you a problem with my 1994 W202 C180 Esprit with about 230 000 KM.
Recently the ABS warning light just appears as soon the car starts moving at certain speed.
Whoever every time I start the engine, the ABS light is off but becomes ON as the car moves forward.
The speedometer is working, therefore cannot be a really valve problem. Could be a speed sensor in one of the wells? Is the vehicle got a speed sensor on the four wells? Or there is a speed sensor on the differential and the front wells?
Please, any help will be highly appreciated
Regards

DGomes