engine stammer while stationery in drive

hi.
im hoping some of you guys might be able to help.
bought a new to me freelander 2011 sd4 auto last year and has been faultless for the last 8 months but over the last month or so has started a rather odd fault.
Only happens when the engine is either tepid , just above cold or if when used and left to cool for a while and then driven again.
while sitting in stationry or slow moving traffic the revs faulter as if about to die then pick up again. .. this goes on for about 10 mins or so till full operating temp is reached.

if driven straight from cold onto a main road where you just cruise until hot .. it is fine and you would never know...

any ideas much appreciated

have booked it in to garage as its still under their warranty but thought id ask here first in case its a known fault thats easily remedied

regards keith

Kind to be a sensor, probably temperature related

A similar thing happens to the D3, which is normally the oil temperature sensor.