Opel Meriva does not start

Hello, everyone; I have an Opel Meriva with A14xer gasoline engine that presents a curious fault: when I leave it in the sun does not turn on and you have to insist 10 or 20 times until it starts; OK drums, OK starter engine, high voltage coil, new spark plugs .... When I turn it on in the morning inside the garage, turn on without problems, if I turn it off after a long route and turn it on it immediately starts without problems if I park it in the shadow it turns more easily. I must add that no failure witness is lit.
If Aguien has any idea of ​​the cause, it would be appreciated.