Josie:

You said:

"... because I went into the office."

I take it from that:

- you're using a laptop

- when you're in the office you're connected to the internet, and when at home, you're not.

If that's the case, I would disable your internet connection altogether when at home. Your computer may be trying to "update" something (as was mentioned) or it is just "listening" for something (e.g. Facebook).

Let us know what finally cures it.
I know a couple of people that are having the same problem.
I'll report back if I hear a solution from them.

Good luck too!
LLOYD S