If the ball and socket connections in your tie rods are worn out and real sloppy, you'll get the front wheels steering on their own (exaggeration, but hopefully, you get the idea) causing the whole machine to be difficult to drive.
If the machine is new to you, also make sure that you have a counterweight in the front. They have to be taken off for various repairs and might not have been put back on. That would definitely cause it to be hard to drive, especially once it starts bouncing.