NOISE ON STARTUP

Hi, have just returned from a trip round the picos and northern portugal down to the algarve and back and everything went brilliant with the bike apart from once or twice when i stopped the engine and then came to restart it there was a loud metallic clang and then it just ran as normal, it has'nt done it since i returned home but it frightned the life out of me first time i heard it, the sound was not tinny or hollow, it was solid and sounded like heavy metal to metal and i'me just a bit concerned that it may be an indicator that something drastic is about to happen, has anybody any thoughts on what this could have been ? bike is an 04 adv with 6000m we were riding hard in hot weather before we stopped both times it done it but dont know if this is relevent.
any thoughts would be appreciated thanks
p.s. bike has run faultlessy since getting home so am scratching my head on this one

Happens a lot - Don't loose sleep over it, carry on as normal

Started my old 1100 up tonight after a couple of weeks lay off OH MY GOD thought the Apocalypse had come Settled down nicely after a minute or so

Mine does that as well, usual followed by another noise..."bollox, work, here I go again!"...