I'm having some kind of issue with my 72" aquarium light fixture. The lights (2 36" bulbs) will come on, but then it will go off, then come on again. There is no flickering at any time. The bulbs are practically brand new, 3 months old or so. And I was having this problem before I put these bulbs in, so the bulbs are not the problem. Sometimes there is not a problem for days, then it will happen again. Turn the light on, it will stay on, then go out, then come back on again. It is very intermittent, no specific times for how long it stays on, or how long it stays off when it goes out. It is very strange. The fixture itself is only about 18 months old.
I emailed the manufacturer (Marineland) about the problem. They said they really didn't know, but that it could be an overheating issue. But that makes zero sense whatsoever since the light sometimes goes out like 10 minutes after I turn it on. They further said it was out of warranty, and that I should buy a new one.

Anyone have any idea what might be going on with it? Or if not, any recommendation on what light I should get to replace it? What I would love to find is a way to just buy the fixture, since I already have the bulbs I want. Is that even possible?
This is for my 125 gallon African cichlid tank.