car shimmies on highway at 60 mph or higher. Can feel it in steering wheel. Could it be a wheel balance problem?
Yes
Yes, it could be a wheel balance problem, but it could also be the result of worn suspension components on your Volvo. This is not something that you should ignore, as worn ball joints or tie rod ends are a safety hazard. Have the tires balanced, and if that does not cure the problem, then have the front end inspected.
Odds are, you have a wheel balance problem, tire defect, bent rim, or something along those lines. Any good tire/front end shop can find the problem and correct it.