Sphero's robot can get stuck sideways in his shell occasionally if you're running certain Macros or working on a Sphero program in development. When you put Sphero on the charger, the robot won't settle heavy side down to charge or shut down.
Fix this by placing the charger cradle sideways on Sphero under the robot. This should power down and reset Sphero. When you wake him up, he'll be ready to roll.