XC60 D5 no power when accelerating

Hello guys, My XC60 has on the last three rides repeatedly it problem that he from a slow rolling mops at about 1000 to 1500 u, turns of the gas lever simply NO Kraf thatte. It is a 2011 D5 with Heico Leistngsincrease. So the car has accelerated quite slowly, but despite full throttle only very slowly. Also take short gas away and then again full throttle did not help. After about 20 seconds the spook had disappeared again – and everything was normal again. The car was warmed up both times. Someone an idea?