Okay, so finally I dived into it myself and fixed it. Apparently if the bookmarks are moved from the root into a folder and from Speed Dial to the Bookmarks folder with the Heart-icon (Looks almost like Speed Dial) it got quiet. So no more unwanted internet-traffic at start-up of Opera (for me at least). Not until I open a web-page.
And yeah this is with Opera 35, I reverted back from 37 for some reason (I forgot now).