Slip indicator light comes on with car NOT on.

I have a 2012 Prius. Just had 90K service. Regular service every 5K and no major problems with the car. In past week or so (about 3 weeks after service) this strange situation occurs. The slip indicator light comes on. Not while driving on slick roads but while sitting in the garage and as I turn the car on for the first time in the day. The light never stays on for more than a few seconds. Sometimes I am unable to get the car to move and have to start the process over. Wondering what is causing this and would it have anything to do with the Prius needing brake work? None has been performed since purchase and the latest service showed the brakes were at 6 mm - front - rear - left - right. Is having this light go on indicative of something serious? Do I need to take it in for service? Thanks for any opinion.