Comment by praash

The balance wheel gets a small energy push through the escapement on each tick. The barrel's mainspring has enough force to just kickstart a stopped balance wheel. The balance wheel doesn't really need much "winding" - it's equivalent to the pendulum of a grandfather clock.

It's really fascinating seeing this mechanism alive, even in a simple mechanical kitchen timer with plastic gears. When wound up, the balance wheel starts to swing a little and quickly accelerates on each tick.