I drive a 1988 Toyota Camry. 2.0 4cyl, automatic.

When I drive, I feel and hear a wobble. It's there whether I speed up or slow down. It's almost like something is off-balance, but I can't figure out what any of this might be.

Would this be something as simple as low tire pressure in one of the tires, or something else?

It is likely that a wheel weight fell off. Also, you may need your suspension realigned (something you should do every several years to save fuel and reduce tire wear).

One of the steel belts in the tire could be damaged. Get the tires checked. It could be dangerous.