This week, after updating my Raspberry Pi B+ (running Arch Linux) to fix the Dirty COW bug, it turned itself off and when I went to check it, it was stuck in a boot loop.
I searched about it and found out that it was caused by a defective power supply. So I just cut the USB cable I was using and soldered it directly into a computer power supply plug (soldered black into black, red into red, ignored green and white wires).
After I plugged it in my Pi, the issue persisted. It boots up, then after ~3-5 seconds it reboots again, and keeps doing this.
What could this be? Could this be an issue with the USB cable I'm using?