This is a qeustion about fat hiding muscle.?

OK i know if you have a layer of fat covering muscle you wony be able to see it....but here is the thing. When i wave or rest my arms my tricipes are flabby and i have "bingo arm". Now when i flew my muscles are toned and my arms donnot shake. My beceips have no problem being toned...relaxed or flexed. But for some reason my triceips look like crap until i flex...then they ovcourse look greart and show off my hard work. Any one have this problem or now why i do?..... oh yeah and i am not fat...i'm about 10-15 pounds over my ideal weight but i'm not fat.