Poser 12 is getting slower and slower, I can hardly do anything anymore, everything takes a lot of time even just moving an object and I'm not even talking about the cloth room. Any idea what I can do ?

Another thing to check would be if anything in your scene has a preview subdivision setting at 1 or above. Subdivision previews slow down the scene. So setting preview subdiv to 0 and leaving  Render subdiv set to whatever it's at should help your preview scene not be so sluggish

I don't know about P_12, but I've noticed that leaving a complex scene up on P_11.3 for several days often seems to slow it down. If I was more confident, I'd suspect a memory leak...

Have you re-booted recently ? ( Full restart, so you get your mobo's splash-screen ?? )

Save scene, clean cache in Poser, exit, restart. I do that if I leave a scene up for days, because I noticed the occasional slowness too if I work on something too long and textures keep getting reloaded.

Rhia474 is right.

Furthermore, it you're on Windows: restart your computer, don't just turn it off/on: restart.
I suspect that it's pretty much the same for most client Operation Systems. I don't trust any OS publisher anymore. Even those damn android-base bloatwares need a good restart, as not a single OS publisher is anymore interested in really optimizing their OSes

I already hear some: Linux: no need, Mac: no need. 
Blablabla: no one is trustable.

The only *nix that don't need a reboot from time to time: servers, as only admins are loging in, and they're doing it carefully.

Thank you for your answers, I tried a little bit everything but it is not conclusive. It's not the rendering that's slow, it's the manipulation in the scene (simple scene with only one character without scenery) and the simulation in the cloth room. Did I miss an update to poser 12 ? Otherwise I no longer have La Femme base in the interface when poser opens, do you know how to put it back? I wonder if not if I will not uninstall and reinstall poser 12.

The latest version is 12.0.1029. Reinstalling might help. You can adjust your preview render settings to help speed up your interface some.

These are what I use and have used for many years and they seem to work well. You can also adjust the 2 settings I marked for even better performance but it looks like garbage on the screen.

To get Lafemme back, you can load her into a new scene and set that as the preferred scene. Of you can tell Posewr to launch the factory default scene. Both would be under edit>general preferences on the document tab

Ah yes I have version 12.0.757 It seems that I need an update, I thought that poserr12 being connected to the web the updates were done automatically. so where can i find the update?

thank you.

Download and install to replace current version, choose to keep preferences when prompted:

https://www.posersoftware.com/downloads

thank you :)