i have a95 riviera supercharged ignition key starts the engine but i have to hold the key in the on position if let it go it turns to off position by it self shutting off the engine also the key is st

It appears the vehicle has a bad ignition switch. On each side of the steering column you will find sunken screws. Removing those crews will allow you to see other bolts/screws to remove which allows you access to the ignition switch. You will need to press buttons/slots in order to remove the switch. I would suggest if by chance you can find a replacement switch in a savage yard, get the entire wirings that runs along the steering column and into the firewall. It seems complicated but its not. Also its suggested, using your phone take pictures to remind you of where things belongs.