> Yesterday I was mowing my lawn and a few of bees started buzzing around
> and bouncing off my head, which  is differrent from the attack behaviour,
> where I get zapped before I have even seen them.
 
Bees do sometimes this when they haven't been provoked lately and aren't
hyped up to sting.  You could also be in a flight path, although there,
you usually will get stung - eventually.
 
Curiously, bees also will *bite* your wrists before they start stinging if
they haven't been disturbed much and are otherwise in a good mood.
 
Allen