Not a charge up in the sense of everyone else's melee.. You can essentially do it over and over and over.. But yes there are some very minor drawbacks to it otherwise it would be WAY too good.

You have to be running for a few seconds and then in lasts for a few more seconds, honestly its good but not extremely good, i main a titan, ik

I guess I never said it was extremely good... Merely stated that the fact that you don't have to wait however long just to get it back makes it quite useful through out a game.. While a Warlock melee you need to wait awhile (depending on Discipline).. I've just unlocked Shoulder Charge on my Titan and I love using it in PVP.. Actually you can easily abuse it once you figure it out.. The shield in front is just bonus..