VW SDI 1.9 motor failure

Hello, I'm new in the forum and I have a Volkwagen with SDI 1.9 engine. I have a random failure of the injection system. When I walk at a certain moment, and it does not always do it, the lightning light of the yellow dashboard is turned on and that has the shape of an engine. It usually turns on when I go to 60 km/h, it shows that the engine loses some power but then recovers it and continues well but with that light on. When I turn it off and leave it from one day to the next the fault is no longer. Could someone guide me? Thank you so much

Friend is best to scanar it and if the fault is not present in a fixed way you will not be able to find it instead the computer leaves it in memory, Czech and the code.