very soft clutch, but only when cold?

I bought a '90 XJ a few weeks back. mechanically it has been running very well, including the transmission.

But on two recent occasions
- both times it had not been driven in a couple days
- both times it was under 40 degrees or so
I went to drive it after startup and could not get it in gear without multiple soft pumps to the floor and jamming it in gear with a minor grind. After driving though, it came back to normal within a few minutes (and as the car warmed up).

This sounds to me like air in the system, but it's odd that the clutch feels fine/normal after driving a bit.

of note: fluid level has not changed at all, and I have seen no sign of fluid leaking anywhere....

:helpme:

Will try a bleed tomorrow and see how that helps.

ick, just looked down in the m/c and the fluid is NASTY. siphoned it out and wiped the m/c inside with a tack cloth...looks like this stuff hasn't been changed in a decade!

added new fluid, so hopefully all will be good when I try it out tomorrow