My raspberry goes to black screen after a while

Question

Well, i bought a raspberry pi 3 model B, when i turn on the raspberry it is all working fine, then after 1/2 minutes, the screen starts glitching, the image starts glitching in waves, like the interference that old TV made when a cellphone rang besides. After a while of that glitch, it starts appearing some horizontal green lines, like burned pixels and the screen goes black. I know that the raspberry still works because the power led and the green led are flashing. Is there any fix to this problem?

Notes: I´m using a HDMI-to-VGA Adapter

SD Card: Toshiba 8GB

OS: Raspbian

Monitor: VGA 1280x1024 Samsung 60Hz

EDIT: So, i really think that is the power supply. At first i thought it was the Adapter, but when recently i was doing my "studys" and i changed my power supply to a usb-to-microusb puggled in a Apple usb charger (i knew it wouldn't enough power and i wouldn't get out of the boot fase) and one thing i noticed was that, this glitch i was having was fixed, i stood with the pi on for about 10 minutes and no glitch. Note: i looks like it is fixed, but i couldn't get out of the boot fase to the OS graphical ambient for lack of power, so i'm not 100% sure if it is the power supply the problem.

Answer 1

I'm using a HDMI-to-VGA Adapter

You have to try it with a normal HDMI display and cable to rule that adapater out; some of them suck power and the pi's HDMI output will not deal properly with that.

If this happens on a normal HDMI display, the pi is most likely defective. If not, the cable is to blame. Besides "loose connection" or "insufficient power supply" (which probably wouldn't result in this, but in any case should be 5V and 2+ amps), I do not think there is any middle ground here.