It happens all the while Iam driven
when u lift up off the gas car will slow down like u are steppen on the brake on 2000 Jaguar Vanden Plas
could be fuel filter issues or transmission as if it's in 1st gear? also check basic filters like air and fuel... less expensive to replace.
I just bought my 05 jag,if it is in sport mode ,u can drive normally ,but the car will de-accelerate quickly unlike if it was in normal drive.