Hi, Simone
A journey is like a pipeline through which the contacts flow. Once in that pipeline contacts will not start the journey again, even if the journey gets stopped. (The only exception would be a recurring journey, where contacts start for each recurrence from the respective segment.)
If you really want to repeat your journey twice without recurring, you can set two identical swim lanes in a customer journey with the same contacts and the same operations.

For example, sending an email to a segment of contacts will be operated twice. There will be warning prompting that ‘This journey uses the same email message multiple times.’ This does not affect it to go live.

A ‘Wait for / Wait until’ can also be added to the second swim lane if you need a time interval between the two operations.
Hope this helps.
Best Regards,
Nya