Actually flashing might be worse...
...but you need to get the fault code red. Search on here for Alfa Diag and EOBD to give you some ideas. Could be any number of things but if I were going to guess, based on your symptons, I'd go with the knock sensor being triggered. That would imply pre-ignition or detonation because of either crap fuel, or the mixture running lean.
I'd start by checking the air hoses and air filter, make sure there aren't any leaks. But it could easily be a tank of rubbish that you need to burn through... have you just filled up?
This is speculation though, you need the fault code read to know why its gone off. I can help if you happen to be in West London.