84 fiero starts when it wants to and has voltage problems

My Fiero has a weird problem it turns over every time but if the check engine light does not come on it will not catch. I can go somewhere fine come out and it won't start but if I leave it for a few hours it will start again. This is one of my pains... Then there is the voltage gauge after starting the car it sits at 12 volts but as soon as I start to drive it goes up and up the faster I go. If I turn my lights on it comes down a little bit and even though I have no A/C belt on If I put it on max it comes down some more. What the heck is going on? PLEASE HELP