Ok, so this is starting to tick me off a little.

When I'm in my throne room I go through all the open job cards, make sure I don't miss out on any problems, try and solve opportunities if I can - the usual. Sometimes there's some time left in the month and I might only ALLOCATE an advisor to a job (pick him in the selection dialog) but NOT start the mission for some reason or the other.

At least three times now I come back to that screen and find that the job was started, even though I didn't click on start.

Has anyone else seen this happening?

The only time I allocate an advisor without starting the job is if it costs BP, and I haven't seen those start automatically. Only reason to delay the others is if the Bald Hill is about to activate, since you need to assign your General or Regent on that immediately and need to have them available (which give no leeway for dealing with them, you need to address it the same day the event pops up or you're kinda screwed). Every other event usually gives a few weeks of leeway to start it, and the only projects that take more than 2 weeks to complete are the curse research projects.

Sorry, this wasn't really helpful, as you seem to be basically saying "Don't leave advisors in job cards that you don't want to start"...

Slightly related: Why do Job cards say "Should be attended before 1 Neth (XI)" but then, come 1st of month TEN I get a "you didn't assign an advisor: FAIL" message? What gives? How am I supposed to plan stuff, when things happen outside of my control?