Some times, especially in the morning, when I turn power on, I see and hear the alert sign (triangle with an exclamation mark) just for one second, than it disappears. I never saw it before. It started just last week. It is useless to go to a dealer because they may not see it when they will turn power on. It is not always happens. Is any body encounter such problem and may know what and why it happens? Is it dangerous?
Not to worry. It just means the self-diagnostics are running faster than other parts of the car are warming up and turning on. Once they turn on, the warning goes away. More common, and may take longer, in colder temperatures.
What is the condition of your 12 volt battery? How old? Possibly the voltage is dipping low enough during the startup cycle to flash the triangle. There are many threads on what happens as the 12 volt battery starts to go bad.