Please help, 1998 318I E36 won't start on hot weather

I live in central west of NSW.Australia
The weather has been rediculous hot.
When i start the car in the morning it was perfectly fine.
But when it gets hot (under the sun) i have to hold the key on the ignition for 1-2 seconds to get it start, after it start its not.
Now it getting worse, sometimes when i turn the key, all the instrument light came on but the motor won't turn at all , not even a click!
Wait till sunset and car cools down, go back to start the car, it starts straight away, no sign of low battery or anything.
No i am trying to put sun shade in front of the windscreen when park under the sun, it helps little bit.
I am thinking, could it because the heat tricks the immobilizer to keep the car from starting? When it not starts up and i pull out the key , the key is really hot, but the dash is hot as well, because we got arround 40 degrees!
Any one have any idea would be appreciate.
The weather has been rediculous hot.
When i start the car in the morning it was perfectly fine.
But when it gets hot (under the sun) i have to hold the key on the ignition for 1-2 seconds to get it start, after it start its not.
Now it getting worse, sometimes when i turn the key, all the instrument light came on but the motor won't turn at all , not even a click!
Wait till sunset and car cools down, go back to start the car, it starts straight away, no sign of low battery or anything.
No i am trying to put sun shade in front of the windscreen when park under the sun, it helps little bit.
I am thinking, could it because the heat tricks the immobilizer to keep the car from starting? When it not starts up and i pull out the key , the key is really hot, but the dash is hot as well, because we got arround 40 degrees!
Any one have any idea would be appreciate.