Deleted

....

...go on?

...ok

So wat?

just don't use auto login never ever on no service / program

Usually, when I open my PC, not a single account can log in automatically. Mostly because of the fact that I took out my GPU and CPU cooler to clean the dust off but hey, there might be other reasons.
Seriously though, Steam might have launched before you PC connected to the Internet. It will always ask you for username and password if that's the case. Also if you have very, very little free space on the drive Windows is installed on(usually C:) Skype will ask you for login data next time you boot up your computer. Don't know if it's the same with Steam but I still wanted to point that out.

if you're going to be this paranoid every time, might as well get that antivirus

which Win version do you have? 8.1 comes with Antivirus.

use that steam protection thingy. yea it's a bit of a hassle to send code to email whenever you're logging in, but hey !

Yes. It is normal. It has happened to me in the past.

Don't open steam anymore then :3