Hi Carole,
I've had a Lyons for decades and really like it. The fan in mine slowly developed a bad vibration during incubation last year. I ended up replacing the fan but there didn't appear to be any negative effects on the eggs. A little hum is probbaly no big deal but I would avoid genuine shaking, and a fan that is acting up could go bad at any moment.
I'd suggest first checking the blades for dust accumulation that could cause an imbalance problem, or maybe a loose mounting bolt.
Lyons (http://www.lyonusa.com/) can provide spare parts and I assume good advice by phone. I ended up getting one at Allied Electronics to avoid the time or air freight from California (but my situation was urgent). The replacement takes a little bit of skill but is not tremendous. It was much easier to have a second person (okay, I admit it, I was the helper not the fixer)
So, I hope to see you show off some hatchling benti in Daytona this summer.
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Lindsay Pike
Urotopia Uromastyx