An easy answer will be, if using RPE, start the next set as soon as you feel RPE 2 or 3...
Calculating recovery heart rate often could also give you a hint of how much rest you need between sets. This should go lower the fitter you get...1-2 minutes sound reasonable for most people, apart from near maximal/maximal efforts.
Hope this helps,
Nik

---

"Discipline is the highest of all virtues. Only so may strength and desire be counterbalanced and the endeavors of man bear fruit."
Nikos Kazantzakis, The Rock Garden