What is wrong with my starter?

Oh my gosh, I can't believe how hard it is to get restarted. I have been away from my trainer since The beginning of July. It has been three months since I had a really great workout. I miss those training days even though I was so from doing them. My little walks or short periods of exercise do not equate to what I get in a half hour of training from my past trainer. Why is it so hard to me to put myself through the intensity he put me through. That is one reason I wanted to go to a trainer. The guidance I received was helpful and beneficial No my progress is very, very slow. I haven't lifted ant weights yet. I am scared to, but I know it is something I have to do.