electronic immobiliser icon flash

hiya, i have a 2003 b6 a4 and ive noticed that if the engine is on but the the car has been static for 5-10 mins, the yellow dash immobiliser icon flashes. the car still drives normally and i can even turn it off and on again to clear it, so it seems it doesnt mean anything. the manual says it only flashes when the car recognises an uncoded key so iam just wondering why it does flash when i am using the correct keys?

try re-syncing the keys....