does it have EFI? or a fuel injected carb?
if you have spark and air then it's gotta be a fuel problem
things to consider and check:
fuel filter clogged?
fuel at the carb?
trash in gas tank stopping up the sock on the pickup?
water in gas?
if electric fuel pump is it working?
check fuse panel for blown fuses? <---this may not apply since it will restart later on.....
if equipt with a fuel pump relay is that working?
these are prolly some of the most obvious things to check if you've got spark AT the plugs.
I'd check the air filter too if you havn't.......
If you have EFI then theres going to be a engine light or something related to that that you havn't disclosed to us yet. ie:a sensor problem? i'm just guessing now.... :)
of course there could be other things too but we won't be confusing you more than necessary at the moment