HELP-woofer moves alot when playing lps

Hi-
When I play a record on my TT, I get an excessive amount of woofer movement, even when no music is playing. When I lift the arm off the record with the finger lever, the movement stops, and the phono stage is dead quiet. Its only when I drop the needle and turn it up a bit, the woofer starts to move in and out. I dont get this when playing cds, only lps. I have my system on a shelves, with the table onto and my integrated amp directly under my TT. Might this be an isolation issue? Thanks in advance.