Engine stalled and wouldn't start

Yesterday I was driving home after work and the engine stalled. Managed to roll into a parking lot, tried starting the engine and the dashboard lights would come up but the starter motor wouldn't even engage. Was hella tired, so I left the car there and went home. Came back the next day to tow it away and bam, it started with no problem. So I suspect it's some kind of electrical problem. Would the engine even stall if it's a faulty starter motor? Does anyone know where I should start looking?

Car: Saab 9-3 2003 2.0T 129kw