Ideally, to check the steering you'll need a helper. If the helper swings the wheel from side to side repeatedly, just enough to start turning the wheels while they are on the ground, you can check for movement.
Common problems are the steering arm on the steering box loose or the steering box fixing bolts are loose, the steering arm on the relay loose, the relay itself loose in the crossmember (seen from below) or a duff track rod end.
All of those can be seen quite easily, and you can feel a track rod end by wrapping your hand around it and feeling for a 'clunk'.
Also check the swivel pins on the hubs by jacking up, gripping the wheel top and bottom and trying to rock it. If you feel movement, try it again with your helper with their foot on the brake - if the movement stops it's wheel bearings. If there's still movement, you need to check swivel pins.
It's also worth checking the axle U-bolts are tight, that spring/chassis bushes are OK with no play and while you're at it - the state of the shocks and rubbers.
If that all looks good, you can tighten the steering box adjustment, but just do it a bit at a time, with both front wheels jacked up. You're looking to reduce the amount of free play at the steering wheel, without it feeling tight when going from one lock to the other.
It's bound to be something in that list, or perhaps tracking which is easy enough to check with a tape measure and a stick
Hope that helps,
Robin.