Macbook Air strange boot-up

I've searched before asking but couldn't find any related question with the problem that I'm facing.

I have a new Macbook Air (1 month) with Yosemite 10.10.1 that from the beginning is having some strange behavior on boot-up.

Specs:

• 1,7 GHz Intel Core i7


• 128 GB SSD


• 8 GB 1600 MHz DDR3


• Intel HD Graphics 5000 1536 MB

When I press the power button the screen remains black (I notice a different black when the room is dark) for more than 1 minute before the apple logo appears and then it's seconds to go to the login screen.

However, when I boot-up with the Alt key, the screen to select the startup disk is very fast to appear and when I select the "Macintosh HD" disk, the Apple logo appears right away and then again it's seconds to go to the login screen.

So basically if I boot with Alt key and force the disk, it is very fast to boot. When I do a "normal" boot, I have to wait at least 1 minute before the Apple logo appears.

It seems to me like an hardware problem, but before I take the computer back to the store, I wanted to make sure if there is something else I should try.

Any help would be appreciated.