A sensor problem?

Dude, l come from a family that owns all kinds of exotic cars. My uncle owns or did own the same Porsche that eventually formed this problem. He got rid of it. Sorry.

It could be residual heat inside the vent cavities, or it could be a delay while the system re-calibrates itself (i.e. getting a valid signal from the temperature sender, repositioning the servo motors, etc.)

l would not necessarily believe that this is a failure, more likely a normal operation.

Sounds like a normal 944 to me. Its residual heat in the venting system.

Porsche venting systems for fresh air sucks and has always sucked--it is just not the car is strong point.

l had a sticking heater control valve in my 968 (very similar to the 944) that caused lukewarm air to always blow from the outer dashboard air vents. The valve eventually blew & a new valve fixed the problem. You may have something similar.

If it is ur heater control valve, the good news is that it is fairly cheap ($40 or so) & can be done from the top of the engine. You will have to get a couple things out of the way but it took me around 90 minutes & nothing was hard to do.