2008 Smart Car stalling

So my car decided not to start. Finally got it to a garage and it was determined the crankshaft positioning sensor was bad. Picked up the car and started right up and headed down the road. About 15 minutes later it died. Phoned a friend to help me get it off the road. As the car sat for a while it had restarted and I got it home. Called the mechanic and said to bring it back. They were closed on weekends so waiting for Monday. In the meantime the car sat overnight and started the next day and ran for a while, about the same time it stalled when I picked it up. What the heck is it now?