If wired, try a different wired headset to rule out break in wire. If problem persists, check for some debris in headphone jack. If problem still persists, headphone jack may be broken or worn out.
The problem with wired headphones appeared after the release of Sony Android 8.0 Oreo. I had the same problem, look for my posts on this forum. And don't listen to some, all you have in order and with headphones and with the connector on the phone. All questions to Sony.
