Lagging render/audio slows

+1 that there's a pretty decent chance your system's audio settings may be the cause here.

- If using .mp3, try a different format.
- If using bluetooth audio device, remove that from the equation. 

- Confirm system-level audio settings are appropriate.

- Recently used other apps that involve audio? Games and video conference apps are both bigtime suspects, as Mylenium suggested. I have a few that will take over my system settings every time, no matter the prefs I've put in place. 

you may face this issue if you're using a .mp3 file, so be sure you're using a .wave file

Without any details about the project, redner settings, preview settings, audio preferences, system info and so on we really can't tell you much. The first thing would be to check those things, clean out the disk caches, tweak the audio preferences and so on. Likewise on a system level you would need to check if you recently have switched audio devices or turned on soem of those crappy "enhancement" features for virtual surround or such that consume resources and interfere with AE. This could even have been caused by a game or some video conferencing software messing up settings.

Mylenium