So I have this weird habit in bed...?

Okay ladies, I have this sort of weird embarrassing habit when in bed. Everything will be absolutely perfect, but when I finish I shake like crazy! My hands and legs tremble and it's like I'm in a state of shock. It's not the usual "shake when you cum" situation, it's beyond that. This lasts about five minutes or  so, and I'm just wondering, is this normal and does anyone else experience it??