Why does my projector suddenly stops displaying anything?

When I turn on my projector, it sometimes works fine initially but after a while, the brightness suddenly drops within 2–3 seconds, leaving the screen blank. On other occasions, the problem is present right from the start—there’s no display even when I turn it on for the first time. Sometimes, I can resolve the issue by turning it off and back on, but other times I have to wait—either keeping it running with no image or turning it off for a while before restarting. Over time, this issue has become more frequent.

What could be causing this problem, and is it fixable?