Same for me, I'll notice my computer is a bit loud, realise I forgot to close postman and it's just sitting there, doing nothing, minimised, and my 12 core CPU is sat at 20%.
I close postman, within seconds the fans spin down.
I've tried a few alternatives but the rest of the team use postman and we've got shared collections and pretty extensive pre-request scripts and nothing else I've tried really fits the bill.
"How many Transporter accidents have there been in the last tens years, Reg? Two... three? What about the millions of people who transport every day without a problem" - Geordi - TNG Realm of Fear S6E2