How many of you take your shirts off when working out at the local gym? There are a few guys at mine that within minutes of starting to work out they have to take their shits off.
Funny thing it, they are usually not in real workout type clothes, something like jeans, etc. Nor are they in any great shape, usually skinny so they have definition, which I guess they assume makes them look muscular.
There is no rule about it, but no matter how big or great I were to eventually look, I would feel funny about taking my shirt off, not out of imbarressment but more along the lines of being a little modest and humble.
I really respect the big guys I see, that come in in full sweats, knock out a hard workout, without a lot of fan-fare and chatting. They are always the ones that seam to be putting the muscle on.