Hi Hyundai

I own a 1999 Hyundai Accent

But I am having a little problem with Vapor Lock in hot Weather. Now it runs fine, even going up the mountain grade. It run fine when the temperature is cooler, 75 degrees.
My problem is when I turn shut it off and try to restart it. It won't start. The engine spinns, but does not start.

I did this experiment:
I took for a drive in hot weather for about 2 miles
When I got home, I shut off the car and then started the car again, It did
I did that three, no problem. Then for the 4th time, I let the car sit for about a minute and tried to start the car. It would not start.

Could this be bad gas?