Im going to say you are in need of a new clutch. If it is an aftermarket clutch that usually means it was driven pretty hard and 88000 miles on a clutch is reaching the end of the life of the clutch life anyways.
It might start working better when it warms up because the clutch heats up and expands causing it to engage better.
You may have old fluid with crap in it or air in the line that keeps it from fully engaging until the fluid heats up.
Whatever the case IMO you will need a new clutch soon, but for now just keep driving it until it is unbearable.