ABS/TRACTION warning lights

[RCS]

I am having problems with these warning lights,I have an Astra SRI 2 Litre, 2000 reg. When left standing for any lenth of time (overnight?), I start the engine and the offending lights stay on,if I turn the ignition of and start again,the lights go out and will stay out until the car has been left standing again .I have changed the pads all round and this has not altered the problem in any way.I have no idea so please help.
Thanks to all

RCS

PS/ After posting this,I tried just turning on my ignition, turning it off again ,then on again. This seems to work and the lights go out.Any ideas please.