Problem with electronic

Hi All, 

I'm having an issue when car (Octavia 2006) is parked outside in hot summer days (35 Celsius degrees or higher). 

Once I run the engine it starts with turning off the electronic devices one by one.

Within 20 seconds the air condition and its temperature display turn-off. Soon after, the right and left blinkers stop working (strangely all 4 are working fine at the same time) etc. until eventually the engine turns off (not always).

Often cannot start the engine again (dashboard has lights and no error indications on it) until it cools down for few minutes or longer. 

No such problems outside summer whatsoever. 

Any suggestion on this please? I tried at the auto-repair shop but they had no clue about this.