1998 VW Cabrio doesn't like the heat. Vampire Car!

Hello All, I have a 1998 VW Cabrio that will start right up in the morning when it’s cool. When I get to work and it sits in the sun for a few hours, it won’t start. All the lights on the dash will come on but the darn thing just won’t turn over. After the sun goes down and I leave work, the Cabrio will start right up. The only thing that I’ve tried is jumping the car and that still won’t make it start. Has anyone else with a Cabrio had this problem? Does anyone have some good advice for me? It’s my only form of transportation and I can’t afford to give this car up. Thanks for anyone who would help with answers. Maybe my car’s a Vampire.