Fluorescent light only flickers when I turn it off
It is one of two problems. If you have another fixture with the same bulb, try switching the bulbs to determine if the bulb in question is bad. If you can't do this, then go to your home store and buy a new bulb (bring the old one with). Try it it the fixture and if it works, great, problem solved. If the problem still exists, then your ballast in the fixture is bad and you will have to replace it. You can usually get those at your home store too and they're easy to replace. The procedure to replace them depends on the type of fixture so we'd need a photo if you determine that's the problem.