P38 alarm clicking

Hi all, I've returned to owning a range rover after a absence of 10 years, i've purchased a mint Xreg 4.0 Lpg HSE fully loaded with oxford leather its done 94000 miles. Everything seems to work but there is one annoying problem on initial start up the alarm sounder clicks until you switch the engine off remove the key and restart its ok then until you leave the vehicle for a period of time there are no fault messages on the dash display, anybody had similar problems?