"MOST" cars have Power Steering that relys on a hydraulic pump driven by the Engine via a belt.
If the hydraulic fluid leaks out, the belt breaks, or the pump wears out the car will be hard to steer
Three possibilities come to mind: # wrong key # steering wheel locked # defective ignition switch For #2, one has to relieve the tension on the steering wheel before the key can be turned.
could be your ignition
The problem could be the lock for the steering wheel. Move the steering either side while trying to turn the key.
Your car may need power steering fluid if it makes a buzzing noise when you turn the wheel.
A shaking steering wheel means something is wrong. Can be a tire out of balance, bent wheel, or suspension problem. Whatever it is, the shaking it putting stress on other parts and can cause other things to wear out. It is especially hard on wheel bearings. have this diagnosed and repaired asap.
There may be something wrong in steering linkage.
It could be the wrong key...not inserted completely (or inserted to far if the lock is damaged)...the steering wheel lock could be exterting extra pressure on the lock (try moving the steering wheel a bit to see if that helps)
Tires out of balance, bent wheel, tire defect, or suspension or steering parts worn.
it could be the shearing pin fitted in most cars to stop thieves breaking the steering lock, could have been damaged when you took it out, or the splines on the lower knuckle joint not connected
This could be a number of items wrong. Typically, the steering column bolts break. There is a "knuckle" at the end, you should be able to look under the hood and see where it connects to. Or, your steering wheel could be loose. Either way, DO NOT DRIVE, until you have it figured out.
There is something wrong with your wheels or steering. You car is NOT safe to drive.
It could be that the steering wheel lock is hung up. Try turning your steering wheel gently from side to side while trying to turn the key. See if that allows the key to turn.