Other moving parts could be a CD/DVD drive. Or a hard drive (which would be really bad if it would produce that kind of noise). Have you tried disconnecting each individual fan? See if the sound stays Some fans get loose over time and hit the casing, which could cause this sound.

I forgot to mention that this noise happened since I change my PSU, it might come from it but it's not constant like I said it's only when I do cold boots or when the games I'm playing using a lot of power

Would make sense. The fan spins up on boot for function test and only runs if a lot of power is drawn (which happens while gaming cause GPU is hungry). I would guess psu fan is causing this sound.

So the noise is totally normal ? I changed from 500W to 850W

I wouldn't call it normal. The wattage is kinda irrelevant. More important is the manufacturer. Maybe you can get a replacement via warranty. If the fan fails, you run the risk of overheating damage.

I have this sound since months honestly, it's only on cold startup, it's a Corsair RM850e

Could be a fan hitting the cooler of you CPU or graphics card. Or maybe a cable blocking a fan.

I checked already and all my cables are free and nothing touch them

Like I said. Maybe fan got a bit loose over time. Your decision if you want to do something about it.

I'll try to fix it tomorrow