Sounds like a personal problem. ;)
What you need to do is drop the reins. Make them as long as you can. Relax your legs. Honestly, he doesn't need your help to move. He can move just fine when you're not on him, I'm sure. To ask to trot, keep your hands down (or on his mane, not the saddlehorn), and do not shorten or move them to trot. "Click" at him and give a small push with your seat if you know how. If you need to, give a quick, gentle squeeze with your calves. Do not kick at him. That tightens your joints and body and makes the horse really not want to move. It might take a few seconds or tries to get him to trot like that, but he should do it. If he doesn't get it, you may kick with one leg, not both, just to get his attention, before going back to asking with your voice and seat.
Do NOT lean forward when he goes to trot. You don't need to and he doesn't want you to anyway.
Once he trots, do not try to correct him, even if he starts out super fast. If you must, post, or two-point. After a few strides, slowly get him under control. Sit tall and relaxed. Gripping just annoys him. If you need to, use two hands on the reins and open them, dropping them down to his shoulders. Don't bother just raising the reins and pulling on them. That annoys him and doesn't really help you.
If you still need help, just get a trainer. It's not really a huge deal. Just ask for a lesson or two. They'll be able to help you out.