Hyundai sonata intermittent no start

My daughter’s 2005 Hyundai Sonata continues to strand her periodically (12 times in the past 18 months). Sometimes weather seems to affect it - warm/hot not good. It will not start after being driven until warm/hot (esp. with air cond. going) and left to sit for a relatively short amount of time. Lights and bells sound, but absolutely no action from engine. If left to sit a couple of hours, it starts as if nothing had happened. Hyundai isn’t cooperative, as it never acts up when in shop. The problem started while still under warranty, but it is now over 6K and warranty is off. Anyone out there ever have similar problem? Any advice?