laptop turn on but no response

My Dell Vostro 2520 (Intel Core i3 3rd Gen, 8GB RAM) powers on, but only the power LED and charger LED (while charging) turn on, with no display. Very rarely, it starts up and works fine. I've tried power draining, using an external display, reseating/swapping RAM, and removing external devices, but the problem persists. The issue is inconsistent, and I haven’t found a clear pattern. Any help would be appreciated!