Body Shudder > 2002 Solara Convertible

My 2002 Toyota Solara convertible appears to have body shudder between 0 and 45 mph. Above 45 it does not shudder at all.

It’s subtle - but - definitely present. The tires are brand new (michelins) and all 4 struts are new (including mounts) - Monroe Sens-Trac.

Is this because the car is a convertible and the weight gets unevenly distributed ? Is there something else i should look for ?