Lag on startup and after unlocking

Before I begin, I know there is a thread with a very similar name, I've read it and unfortunately it was of no help - my problem is not the same.

Ok, so this computer is 3 days old, and until today it was working very well.
It is an Acer V3-571G. Intel i7, 16GB RAM, Nvidia 730M.
What happens is that every second shut down and boot, the computer freezes while booting and I'm forced to force shut down. The second boot works but takes around 2 minutes and unlocking takes around 30 seconds. After unlocking everything is slow to load, even right clicking the desktop takes 20 seconds to open up the options menu (the one with personalize, screen resolution etc).
After its initial "preparation time" it gets back to full speed and works like a charm, but its really annoying to have to deal with slow boots and only being able to boot every second time.
I have very few startup processes, all of which are either intel, microsoft and nvidia related. The only 3 third party processes are steam, avast and mcafee.

I would be glad if someone could help me.
Thank you very much.

P.S. I don't have a windows 8 CD or a system restore point.

EDIT: I have to go now so I probably won't answer. I'll check back whenever I can.