Also possibly the issue may be connected to the temperature. I mean there is a chance that the board starts fine only if it is warm. So please try to warm it a bit with a fan prior to cold start.
It has nothing to do with the temperature. As long as the power-on interval is short, the board can be started. Only when the first power-on or the two power-on intervals are long will fail.
What's more,it's better to make sure the uboot is proven correct and the DDR hardware is reliable.There is a risk if the DDR is not assembled appropriately which may cause failure everytime the AP try to access to the memory and consequently the system halt.
