^^^ This^^^ And note the 4th line in my signature.
If you think about it for a second, look at all the sophisticated electronics that operates out in the cold. Our cars are full of computers and they sit out in sub-freezing weather (and extreme heat) and still work fine. Street/traffic light control panels are outside, along with all sorts of other electronics. Obviously avoiding exposure to direct sunlight in the hot summer, and wet conditions is necessary. Beyond that, electronics can tolerate a pretty wide-range of operating "temperatures".
Humidity
in the air, even at 100% is not a problem either. As long as the electronics are not "wet" that's fine. In fact, the advantage of humid air is a less or even impossible chance for ESD (static discharge) issues (except from Mother Nature).
A rapid change in temperature is your greater concern.
Will it be better to put it out and let it cool to the room temperature 28c - 32c before boot it up ?
Cool to the room? That suggests it is currently hot. Is that what you meant to say? Or did you mean to let it warm up to the room temperature?
Either way, it is always best to let any electronics "acclimate" to the ambient (room) environment before applying power - particularly when going from extreme cold to warm, such as when coming from the very cold outside in the winter to a warm room indoors. This is to avoid condensation, as mentioned earlier. But seriously, 16°C (60.8°F) is
not "cold". Some would consider that barely cool. And it is unlikely your ambient (room) temperature would even be considered "warm" by most people.
And besides, you said this device has been stored under the motherboard. So that suggests it is already acclimated to rest of the equipment.
Should I add some food grade silica gel to prevent moisture ?
No. Never!
