Do you live in a place with lots of humidity?
I live in Dominican Republic, it is really hot at this time, but i can't say it is humidity.
Ok listen, I asked you this because I live in the caribe as well and I ve seen this problem 100 of times. The salt eats the motherboard and teh power supply and the electric fluctuations ( at least here) are poison for the power supply. In most of the cases, changing the power supply fixes this issue. In some cases the motherboard itself gets damaged. I suggest you to change the power supply to one at least 550 watts, more watts would be better, like a 700 watts. This is the cheapest option. If this doesnt work, then you have an additional power supply as a backup for future problems and then the problem is in your mother. What I do is, remove the motherboard, get a magnifier (lupa) , amd check closely specially the back part of the motherboard and see around those dots of soldadura if there is around them something that shouldnt be like a creamy color ring or green color ring, if you have that, then is time to changde the motherboard cos the corrotion made its work there and there is no way back. Always use a UPS if there are electrical fluctuations in your country and be sure all inside the case is clean and free of dust. Dust can lead to serious motherboard problems. I fix computers here and is unbelivable when I open some computers what I see inside, all covered with dust, spider nets, dead roaches, dead gekos, etc.
Try changing the power supply and let me know.