turtle care

Hi, I found a baby terrapin in my garage over the summer. It appeared to be newly hatched. Actually it was the size of a dime,upsidedown,and full of saw dust. I thought it was dead. I took care of it all summer and fed it baby turtle food. (she ate very well)I live in southern new jersey and I have the river on the corner of my street. I was hoping to care for this turtle and then let it back into the marshes when it was big enough to take care of itself.On nice days I would leave the turtle in sufficient surroundings outside and then bring it in at night. I obviously can’t do that now because it is too cold outside. I have her in a huge tank and bought her a uv lamp and a heat lamp.My problem is that all she wants to do is sleep. I was told that she is hibernating and that that is normal,but she is soo small (the size of a quarter) Is it o’k for me to just let her be? She also seems to have a covering over her eyes but it goes away when she is in the water.I was really hoping to care for her and do the right thing but I need to know what is best for her. Can someone please e-mail me with some info. Thanks TERRY