Mysterious engine behaviour

It’s a Laguna I Grand Tour, Motor 1,9l DTi You don’t know how to drive on a normal road and everything is fine. Then, from one moment to the other, the engine starts to run very rough… you might think he lost the oil draining screw. then, about 2 seconds later, the engine gives full throttle without anyone stepping on the gas! After the shock, you start to react…Bremsen… Kick the clutch… The following vehicles disappear in a white wall, so the car smokes. On ignition keys slightly turn back zim motor shut down no reaction.. So the 2nd gear in and the car brutally braked down and strangled.. A look into the engine room shows that it was sprayed around the area of the battery oil.. also drips some oil in this area on the ground. Now you could guess engine damage odda other things…. N and the best: about 5 minutes after that happened we just turn around the zünschlüssel – he jumps immediately without a sound… then squirts 5 – 10 seconds like sow and that ends then. And so he drove the 40 km with different stops well home as if never had been anything! Does someone have an idea now what that could have been? At this event my wife said that he would have done that before 2 years ago… Gruss Marco