Suspension going to Extended Height by itself

From last few weeks the suspension is going into 'extended height' automatically. I will leave the rover for day or two in the garage and it the top light will blink and the height will go to the 'extended height' level and will stay there until i go to the highway and it will come back to the normal level. Today i was driving in the town and it went to the extended height level and the top light started blinking for a while. I stopped and manually lower it the normal height. Any idea what is causing this?
Thanks in advance.