Right, this pops up on a regular basis as a query, There seems to be no definitive answer/reason for it. One remedy which has been mooted is to turn the ignition to "off" and waiting a few seconds before trying the ignition again, and it invariably works for what ever reason. Well we are not alone in encountering this occasional blip. Below is a query from a truck forum regarding a Daf LF 55.220 Euro4 2007.
One of the replies/remedies is the following
"mine does this occasionally , simply switch ignition off give it @20 seconds and try again . sorted ! DAF seem to think its a sensor error and if it happens in their care they will be able to look into it but murphys law states it will perform perfectly while they have it"
From here
The TruckNet UK Drivers RoundTable • View topic - Daf won't start. Engine Warning.
So next time it happens take heart in the knowledge that you are not alone and take solace from the fact that you are driving something a little less expensive than some other people who are also experiencing this mysterious glitch.
Think it is time to involve Prof Brian Cox and try to get to the bottom of one of the great mysteries of the universe...