Build help

Hello, i'm new here i just wanted to know if someone can guide me to a name or to something i can go and see if i can build this little project:

I have a gps (from china) that i need to use on the car,
the problem is that i need it to turn on when the car accessory (or engine) is on, but it has a button (like a cellular) that you need to press like for half a second in order to turn it on.

I tough i could use a relay or something like that to do this but i don't know how to send that "signal" for that half second.... and then stop.
anyways it will have to do it every time the car is turned on.

Thank you.

Can you get inside the GPS and wire to the terminals on the back of the built-in push switch? Are you powering the GPS directly on the car's electrical system, or through a DC adapter which reduces the voltage to ~5V?