What would make a car stall at different times and location but be okay at other times?

I can't say for sure, it could be a few things. You might not be getting enough gas or oxygen into your engine at the right time, a spark plug could be bad, or something in your starter could be bad. An engine only needs a few things to run, the first is enough fuel and oxygen, usually at a ratio of 14/1. The second is a spark to ignite the fuel, and the ignite the spark there has to be electricity flowing through your alternator, distributor, and spark plug wires. So something in that system isn't working right if your car stalls. I hope that helped.

My car had the same problem and it turned out that I had a bad sensor.