That's pretty clever. Maybe that should be changed though... :)
Yeah, it's probably a glitch, but it's still cool.
You'd be surprised to know it's not random at all. It gathers energy from heat, pressure and energy particles and when those values reach a limit, it releases the energy in the form of heat (while glowing) and it explodes.
When a lot of energy (particles,heat,pressure) is applied to it, it stores it as its life. Essentially a time bomb for lack of a better description. I'm not quite sure about thelife-cap, I think it glows when it is 750 frames from exploding.