Husqvarna YTH 150 sounds like it is chugging on cold starts, and after refueling after its run out of fuel. It only does it for maybe a minute, then it idles fine at high throttle, what can be causing this.

Hi,
Only a few things come to mind - sticking automatic choke(if it has one), partially clogged air filter or fuel puddling from a bit too much choke when cranking.
Peace,
Clarke