1998 accord vibration with acceleration
 

Just noticed today; ...my 1998 Accord EXV6 121K miles timing belt 100K
miles, new lower ball joints last year. The car vibrates...actually shakes
what feels to be side to side during medium to hard acceleration. NO
symptoms during coasting, transmission shifts fine (that too replaced at
~85k miles). Brakes fine steers fine.
Plugs, wires, distubutor?? Idles normal not rough. Hoping it is not $$$.
Any ideas??
Thanks,
Matt