I have a golf 2004 TDI.
Recently I have experienced chugging. It is chugging sensation like it is in 5th gear going 15 mph except a little more extreme. It happens in all gears.

It is intermittent, sometimes does it sometimes does not.
When you get past approx 3000 revs it is fine but the car is still not at its full potential.
Sometimes the problem is temporarily 'fixed' by turning the engine off and on (usually when the engine has heated up a bit).

does anyone know what this could be?

thanks in advance