Confusing pop-up

Hi,  I've just had a pop-up on my PC (running Windows 7) that requested I restart my computer. The message appears to be from Norton Internet Security and reads "You must restart your computer for your Norton product to begin protecting you." The thing is, I have done nothing recently to prompt this message and I am a third of the way into my current subscription.

Is this message from Norton? I've had a quick look on this site to see if this is some sort of update but I did not see that.

When I open Norton on my PC it appears to be behaving normally with no updates required. If anyone knows what this is I'd be grateful to hear as I would like to turn off my pc at some point and I don't want the restart to initiate whatever this message intends- if it isn't relevant to me. 

TIA