Weak Clutch at start

1994 Acura Integra LS, 122,000 miles. Recently I just replaced a slave cylinder on the Integra, bled it fine and installed properly. The test drive went smooth, and I felt a sense of accomplishment that it works! Well when I let the car sit for a couple hours, the clutch seems to loose pressure for a couple minutes. Once I shift a couple times, usually by third gear, its builds pressure back up and is fine for the rest of the time being until it sits again. The fluid is at the same level so I don’t think there is a leak. There doesn’t seem to be any damage to the slave cylinder so I have no clue. Can you guys please help me? I would really appreciate any advice, Thanks!