engine just cut out

[Volvi]

Yesterday I had to go into the city, parked there 1.5 hrs. then back home. It got to 38 degrees, just as I rode down the pathway of my home to garage the engine suddenly without any splutter or warning cut out. Tried re-starting but wouldnt fire up. walked it into garage and said aint gonna bother now, to hot will see in the morning. In the morning a slight hesitation in firing and like fuel starved initially but got going after a few secs. idled ok in garage.

So what could it have been? air bubble from heat? vapour? tank was quarter full and Im running Ultimate 98.