Hot and Cold

[echo6]

I have a 98 VW Jetta w/2.0 ltr engine. It runs great.

Here in Phoenix it gets hot in the day time:
Early morning and late afternoon it cools down considerable.

My Red 98 VW Jetta refuses to start in the day when the air is hot.
My Red 98 VW Jetta starts just fine when the air is cool.
Early morning and late afternoon.

What to do
What to doooooo

Should I repaint the little guy, or could it be a more sinister problem……

Any ideas out there…..