Mine does this too, even when I have the Task Scheduler turned off.    

I want to choose when I update, I dont want it to do it automatically at log in, so this is super annoying!.

Yeah, that does seem annoying. 

I haven't dealt with it yet, but I always get the Windows prompt for 'Do you want this program (ProSeries Updater) to do stuff to your computer?' and you can say "No".

On the other hand, I also think it is annoying to log in, then update, then need to log in again.  That drives me crazy.