Arduino resetting and pulsing LED?

Hi, I've got an Arduino project with some TLC5940 LED driver ICs connected. When I start it cold, it stays on for a couple minutes, but then the LEDs will shut off, the Arduino's LED will pulse for about 5 seconds, and then reset. Then it will continue to do this reset behavior every 5 seconds or so after that. It sounds like a temperature problem, but I've checked the temp on all the components and they're either cold or within operating range.

What does the behavior mean when the arduino randomly resets and starts pulsing the pin 13 LED? Is that some kind of troubleshooting code?

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It's a pretty simple setup--7 TLC5940's daisy-chained to the Arduino pins. They and the Arduino are powered by a 7805. 12V input sources the LEDs.

The code is simple as well, there is no loop code. Only setup code telling the TLC's to set all channels to half-brightness.

I think I fixed it! Reseated one of the chips on the pcb and fixed a short, I think.