Q: Car randomly stalls out at stoplights, and sometimes won't turn over. If I leave it alone for 20 min, car will start again

Hi There, What you are describing sounds like an ignition coil pack that may be failing. Ignition coils are prone to this type of erratic functioning or heat cycling when they are beginning to fail due to the temperature fluctuations under the hood which ultimately cause them to shut down causing the car to only run after cooling down for 30-40 minutes. Ignition coils are coated with a varnish-like insulation that becomes brittle over time after being stretched then contracted repeatedly The insulation develops small fractures that open when heated and close when cooled. When open, they allow shorting of coil windings and decrease or eliminate the coil’s ability to function. This process will repeat itself continuously until the coil ultimately fails completely and must be replaced. I would recommend having a professional from YourMechanic come to your location to diagnose and inspect your ignition system.