A couple of things to think about:
Does Windows Task Manager indicate what the PC is doing when you get that lag?.
If it is Photoshop , is there any common activity that is triggering it?
Have you got plenty of scratch disk space (even with plenty of RAM, Photoshop does use it) ?
Thank you Dave. After checking Task Manager in the moment of the lag spike, i found out Malwarebytes is causing the lag. I never had problems with this, and i used Malwarebytes since many years. But somehow there was an update i didnt recognize and Malwarebytes now creates lagspikes in Photoshop... :S