2004 avalon steering is stiff

My 2004 Avalon XLS 101K miles has stiff steering in the past few days. Sometimes it feels fine and other times it gets harder to turn the
wheel. When it's acting up the steering wheel won't return to center after you make a turn either.
I have an appointment for Monday with the mechanic to check it out. Anything I can do in the meantime to diagnose it myself?
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