Fabia mk1 power steering

Had a new steering pump fitted just over a year ago, new battery, always kept fully charged.

dont use the car a lot now, but have noticed turn ignition on power steering light goes out all ok.

have had the odd time light comes up when driving but does go out

left home yesterday, 36 mile round trip, after around a mile the light came on and remained on for remainder of journey, steering all ok light and responsive 

Return home, all ok, light never came on at all

I am puzzled, would welcome anyone’s thoughts on this please