Brake Light

ok i have a 99 Osmobile Intrigue, recently when coming home from work at night, my brake light wants to come on as im speeding up, then as i slow down it shuts off, this only happens if i come to a complete stop then speed up, not if i slow down in the middle of the road and speed up again, it just seems to happen when i stop at a stop sign or something then speed up again, i got home checked to make sure there are no leaks and i checked to see if i was low on brake fluid, cause i know thats what that light means. It doesnt seem to be low. Im almost postive its nothing to worry about, im just trying to figure out why it comes on only at night and then shuts off again as i slow down. sometimes it doesnt even come on when i stop and speed up at a stop sign, its weired. Maybe its just because its the brake fluid gauge that tells you need brake fluid doesnt work right idk? Remember it has never has come on during the day just the night, again its something that comes on when it feels like it seems, i have just noticed this in the last day or 2, so i dont know? Any Thoughts?