Sorry, can't be done. You can set ships to automatically capture any ships and/or bases that spew forth from a planet, but you can't automate raiding the planet itself.
I'm assuming that you're trying to soften them up for a pirate base, so I'll refer to the Pirate Tips thread for this: Pause the game, grab your construction ship, and tell it to move to the planet. Then right click on the planet, select "queue next mission" and tell the construction ship to build a Defense Base over the planet. Now go to the construction ship, cancel the current mission (i.e. moving to the planet) and then unpause. The ship will immediately go off to fetch materials for that new defense base.
Once you've got a defense base orbiting an empire world they are going nowhere. They'll be unable to build any starbases or launch any construction or colony ships. They have been all but removed from the game entirely by this one simply action.
Why mention this? Because once this is done you can take all the time you want to bomb, raid and build on that planet. Plus the defense base itself acts as a ship presence, which reduces influence decay (and can even increase it on very tiny populations). So yeah, it will still take a while to get all the raids done (it's 2 minutes per pod cycle, IIRC) but now there won't be any pressure.
Of course you could just be raiding for race-specific technologies, and that's fine - this method works just as well for that, too. Better, in fact, as you won't be accidentally wasting any pods capturing incomplete constructions ships and space ports over & over (the base just blows them up instead).