@Lohcaiz It sounds like your best bet for this would be to utilize the Newman runner, if you havent yet.
If your collections can run in parallel with no need to interact with each other then this would be the ideal way to make this happen. I have done something similar in the past to help simulate a lot of traffic.
To do this I simply created a bash script and added the command I would to execute the newman runs in as many times as needed.
It looked something like this …
#!/bin/bash
newman run postman/smoke-test/collection.json -e postman/smoke-test/environments/staging.json &
newman run postman/smoke-test/collection.json -e postman/smoke-test/environments/staging.json &
newman run postman/smoke-test/collection.json -e postman/smoke-test/environments/staging.json
This basically kicks off 3 runs at the same time, executing the exact same collection against the same environment. Not perfect by any means but got the job done for me.
Hope this helps and let me know if you have any questions.