They can mean practically the same thing in some situations. For example, if someone puts their hands on you in a way that makes you uncomfortable, then either of those instructions would be suitable and mean practically the same thing. But technically there is a difference in meaning. "Don't touch me" literally means "do not touch me" which means now and in future. It does not suggest you've already been touched, but you may have been. And it does not say how you may be touched, it just means don't touch me in any way whatsoever. "Get your hands off of me" is a bit different, as it implies someone has already started touching you, specifically with their hands, and it's specifically that form of contact that you demand they stop. So, this is a bit more of a detailed instruction, which may be a significant difference in some situations, but in other situations has negligible difference.