Voltage stabilization on power up before booting

[mx270a]

I have some NANO54415s that sometime don't boot when first powered up. If I pull the power cord from the carrier board and plug them back in, they boot fine. Power is coming from a 120vAC to 12vDC power brick, then to a 3.3v DC:DC regulator. I suspect the fraction of a second it takes the capacitors in the power brick to charge is enough to make the NANO unhappy. Is there a simple way to delay the boot up by 1 second - either via software, or via an external chip that holds the reset line low until the voltage has stabilized?

[pbreed]

99% sure this is a hardware issue related to a insufficient pull up we found at low temperatures.
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