97 Crown vic w/police interceptor

My 97 crown vic starts fine sometimes, but if I go somewhere, when I try to get in to leave whatever store I'm at, it usually won't start back. If I let it sit for a few hrs. It usually starts right up. When it won't start, all it does is spin, like it's going to star, but never does. I've had it towed to my house 2 times and both times, it started as soon as tow truck left. It's like. As soon as the engine gets good and hot, it won't start again, till it cools down. It just spins. Please help! The check engine light isn't on and everytime I take it to a shop, it starts right up for them. They tell me they can't tell what's wrong with it, till it won't start there, at their shop.