Vauxhall Vectra spanner through car light

After driving about 6 miles the spanner through car light comes on for about 5 minutes then goes off this happens in the morning going to work and again after work, it always goes off when climbing gradientso,sometimes it doesn't come on at all. It doesn't make a difference to hold the car drives,however I have noticed the occasional slight judder. I have plugged in my code reader but no codes have been stored. Can anyone help.