My girlfriend asked me to leave her alone for a while. Why?

It was only "out of the blue" to you. I'm sure she had been thinking about it. If you asked her and she didn't tell you why, I'd prepare for a break up. We clearly have no idea why she did it. To give direct answers would only be guessing and that's not helpful.

Sometimes people just need space.

Maybe she found a new guy.

There is another guy that she thinks she has a shot at. You were just a Plan B guy and now that an A list guy is in the picture, its time for her to trade up, however since she might fail at keeping this better guy she want you in the wings to go back to.

Usually that is code for "I want to get it on with somebody else but I'm not sure how it'll work out so I'm not officially breaking up with you YET."

Maybe she wanted to do something private like shower or use the loo, so didn't want you around being a pain.

Are you being too needy, demanding or controlling, or you can ask her why she needs her space

She wanted a shiit??............

You should be asking her, not us. We can only guess.

How should we know? Ask her!