What is it called when you're in a state during sleep where you cannot move but partially conscience?

Usually with enough strenuous thoughts ravaging before sleep, when I fall asleep anyways I sometimes go to the state of deep sleep, then back but my body hasn't responded to it. So I'm still conscience of and all I can move is my eyelids and my breathing rate, but as I'm conscience I realize how slow my breathing rate is then I start panicking. So I try to trolley the breathing to get it faster and faster then I'm finally in control. This happens a few times and I hope it doesn't happen again. So what exactly is this?