The Early 2008 MacBooks seem to have a higher instance of having the backlighting go bad from my experience in working on them.
Usually this is caused by either the inverter cable or the display cable/panel going bad. The inverter cable is tucked right under the hinge on those models, and when the screen is opened and shut a lot, it creates tension and eventually wears out the cable. It's kind of similar with the display cable.
Usually symptoms will include the display going dark at a certain angle or if the display goes dark when the computer is bumped, moved, etc. the inverter board could also be going if it's intermittent with no motion.
It sounds to me like the inverter cable, inverter board, or display panel is the problem with the computer. The first two are not too expensive to fix (but do require a lot of disassembly), the display panel is not unfortunately. But there usually isn't a good way to tell unless the computer is taken apart.
My best suggestion is to take your MacBook to an Apple Aurhorized Service Provider or an Apple Store. They will be able to tell you what the issue is, and hopefully it's not the display panel. :-)
I hope this helps!