It's tough to say wo experiencing the shake firsthand,but usually I see prob in the frtend.does the wheel shake in your hands or does it seem completely separate from steering wheel?I've seen bent wheels,lots of tire imbalance,shocks,cause problems.can you push outward from in-between drives and see a lot of play?
Also had one where the leveling valve was inconsistently not holding level and would cause intermittent shaking but usually did it on decel.this seemed to be more of a problem on volvox at the time tho.