Stop/Start Function

Hi, When moving away from rest my 2006 Prius engine cuts in almost immediately and continues to run at a fast revs when I stop, for instance at a junction. It used to gently pull away from rest on the electric motor for quite a way before the engine cut in and the engine used to cut out as soon as the car came to a halt. The car has covered less than 30,000 miles. Has anyone experienced the same. Any suggestions ?