Power On -> Rx goes online and wait until a valid Tx signal - during that time all servos stay powerless
After Rx knows the neutral position of each server it begin with a slow travel to this position.
The Rx does not have the start position of the servo it's enough if it does a slow travel to 1,5ms (middle) or (better) to the neutral position definied by the Tx.
The RX can't switch ON or OFF the power. It can only not put out an impulse signal. The power for the servos come on as soon as the RX becomes power.
What do you mean by "slow travel"
What is the impulse time it should output FIRST????