When you pay a Monero address, you actually use that Monero address to generate a one time address known only to you and the recipient.
Which means that I can give you the primary address and it will generate a new address behind the scenes for every transaction?
You can do this using the main Monero wallet CLI or GUI. What software are you using?
This:
https://www.getmonero.org/downloads/The problem is, I run a node and this is where I have my wallet. So my wallet is online all the time.
Perhaps create a wallet on another device, sign the TX and then import it to the node's wallet to be broadcast ?