Pressing the reset button will not have a known effect unless the power supply is within the range for proper operation (3V or more for the CD4017).
When the power is applied the state of the flip-flops in the 4017 is not guaranteed. It may be anything (probably there is some small asymmetry that will make it non-random). To reset it you should have a sufficiently long reset pulse applied after the power rail reaches operational numbers. This is often done with a supervisory chip that contains a precision reference and a timer.
A poor method is to use a capacitor (for example across your switch) which will reset it if the power is applied cleanly but will fail in many other cases. Amateur and cheaply built consumer devices sometimes have such cruddy reset circuits and they often cause problems for the end user.