For months I found sex could exacerbate symptoms (tinnitus in particular). It's better now, but I still have to be cautious. I would treat it as any other form of exertion during PCS recovery - start at zero (or near-zero) and gradually increase it while avoiding symptom exacerbation. If you're having problems, back off until the symptoms recede, wait as long as necessary, then gradually start to build your way back up.

As always, the goal should be to remain sub-threshold of symptoms as much as possible to promote recovery. One of the hard things about PCS is there is no "I want/should be able to do this, therefore I'll do it." You have to respect the limitations imposed by your injured body/brain.