Sounds like sagging rear springs to nme. I've repoaced rear springs in two 240's. Never had a 240 more than 10 years old that didn't need them (have two others now that need springs; just haven't gotten around to it yet).

It's a medium-difficult job for a driveway do-it-yourselfer. You need a 1/2" drive socket set and a couple jack stands, or a spare jack or two. Both times I did the job, I used progressive coil springs, but next time I might just use standard or "heavy duty" springs as they seem to be more available right now.

If you do it, you might want to replace the shocks at the same time, as - if I recall - you need to remove them anyway to replace the springs.

Check out ipdusa.com or fcpgroton.com for parts. fcpgroton is very reasonable.