2008 Altima Coupe....My brake light has recently come on....only for a second or two and then doesn't come on until the next day....again for only a second or two

Never let those hacks get near your CVT! Just look at the brake fluid reservoir to see what the fluid level is. There will be a line or two on the outside to show you where the fluid level should be.

my fluid is at the minimum......should I add more?

Yes. It is probably right at that point that is triggering your light but not at every moment as you drive (turns, uphill, downhill, etc). Add fluid and I'll bet your light stays off. If not, have another shop look for a minor leak. Maybe a worn wheel cylinder.