Is it normal to obsessively sniff cheese?!

is it "normal"? no, and by asking this you already know.
is it bad for you? No. Unless you are sniffing other people's cheese, or the sniffing activity interferes with other things you want to do, then I suppose it is odd, but harmless ocd behavior. If your activities are interfering with your life, or causing problems in your life, then it is time to talk to a psychiatrist (important because they are also doctors) and you can get some help.

I got to admit cheese does smell good, I really can't see it being any harm, sniff away!