1992 Acura Integra Car starts but will not shift into gear

My car started acting up by slipping when in reverse and 1st. Then after sitting for about an hour it starts perfectly in neutral, just changed the starter 2 or 3 weeks ago. Once it starts it's fine, until I try to shift into gear. It will not go into 1st or 2nd, only 3rd to reverse and when I get it into gear it stalls out. When the car is off it switches to all gears smoothly, but trying to start in any gear causes the car to violently buck like a horse, turning over as if to start, going forward or backward depending on the gear. The pedal is very stiff compared to the day before, and does not fully engage when I press it. I heard it may be a safety switch, but do not know which to check. I know of one above the clutch pedal and one that is supposed to be by the shifter under the center console. If it is under the console, how do I locate that switch? Are they simple switches to go off on position or will it be a more technical job of repllacement and things of the such?