keeping a burger warm until served ??

[Saltire]

Anyways, this isnt so much about a recipe, its more about asking a question.

question is >>>

You have the burger grilled with cheese on etc, its ready and waiting.

You stuff the burger buns in the grill or oven to heat (not toast), ok.

Then once the buns are nice and warm and just ever so slightly starting to firm up, i take them out the grill.

straight away i apply the amount of mayo and relish to the inner surfaces of the buns, just as thick as you like, just like buttering them with the stuff, but thicker, know what i mean ?

Then try as fast as possible to get some salad etc onto the buns and place in the burger and then more salad etc on top of the beef too.

BUT, and this is the bit that keeps annoying me, by the time i serve the burger up, the thing seems ~~~~in cold, not freezing, but getting cold.
I know its natural if your using stuff like mayo and relish from the fridge that you can expect it to be a little cool, but mines always seem too cold in my opinion.
in restaurants etc they seem to be able to get the stuff to ya before its cold, but how the ~~~~ do they do it, does anyone know ???

Apart from that the burger is absolutley mouthwatering, especially when done with a couple of small nice strips of bacon ontop too, damn it !! i forgot about the bacon tonight, LOL.