I have a problem like this on a 2000 focus.
Basically the first time it happened I was driving on a motorway and ALL the following things happend all at once:
-radio switched itself off and needed the code to be re-entered to get it to go on again
-all the dash board warning lights go on and off
-the "bong bong" noise which is supposed to tell you you've leaft your head lights on (when the door is open) sounds, even though your doors are closed
-the cental locks go on and off again and again
Its was happening again and again for about a few months in an unpredictable way
- although it seems more likely in low temperatures. This happens either for a short period of about 5 seconds or for a longer period of about 30 seconds when the car starts to slow down as a result, and even comes to a halt on occasion. . Latterly the car would do all this when you tried to start it - and then you had to leave the car to rest for 5 minutes before trying again.
Scary and annoying.
The RAC man told me it was a battery fault and put in a new battery. In fact this helped a bit in reducing the severity but the problem remained especially when starting the car.
The Ford garage put it through its computer disgnostics and charged me £100 for "fixing" it, but actually this made no difference - the problem remained.
Then about a few months ago the problem seems to have gone away for no reason.