This might seem like barbaric question, but is it possible to bring refrigerated biga up to "frisky" temperature in a microwave, without damaging it?  I'm too impatient to just let the warm room take care of it... Thoughts? 
Yes, but the trick is not to have the dough in the microwave when it's on:   place the dough into a wide, shallow bowl, and wrap it tightly with plastic wrap. Fill a microwave-safe bowl with water, and float a toothpick or a grain of rice in it. Microwave the water 'til it's boiling. Place the bowl with the dough above the boiling water; the water level should not touch the upper bowl. Close the microwave and wait.   (the plastic wrap isn't absolutely necessary ... but it prevents you from steaming the outside of the dough, changing its moisture content)  The toothpick (or similar) is necessary, as it prevents the water from heating above its boiling point and spontaneously boiling when you nudge it.. 