Won't boot on anything but USB power

[thidarknes]

Hi,

I'm a software developper and a beginner in electronics.

I got myself an ESP-WROOM-32.
I'm doing all my test plugged to my PC, for power and serial monitor.

But if I try to power the board throught its 3v3 or 5v pin, it won't boot.
The red led keeps blinking and the code isn't running.

What am I doing wrong?

[ESP_Sprite]

What do you use as a power supply; are you sure it's capable of delivering enough current?