I had a similar issue a little while ago on my 156 Q-System.
Weather wise, it was an awful night (typical break-down weather!) I'd driven to my daughter's with no issues and was there about an hour before attempting to leave.
The engine fired up OK, but the engine management light was on and no throttle response whatsoever... she was just sitting there happily ticking over on idle.!
While I waited for the RAC to arrive, I had a quick look on the forum to see if anyone had experienced the same problem... someone had!
They recommended checking a plug and socket under / behind the glove box; it's the cable that runs from the throttle peddle potentiometer.
When the RAC guy turned up, first thing he did was to connect his laptop to the diagnostic socket and promptly informe me that "It's your throttle body mate, that's gonna be expensive on this, where do you want me to tow you too?"
I mentioned that I found a possible cause on the Alfa Forum... his reply was along the lines of... oh no, not the dreaded car forums... but he said he'd check it while he was there.
He found the plug and socket and to his surprise, found that a couple of the pins within had that slightly greenish / corrosion look about them.
He cleaned them up, gave the plug a shot of switch cleaner and pushed them back together.
On starting and hitting the throttle peddle, we were greeted to the lovely V6 growls!
He was quite amazed, so much so that he updated the RAC database there and then!
Defo worth checking yours... especially with all the damp weather we've had!