I had AFIB for a while, most of the time after eating and sometimes not.
I decide not to eat after 7.00pm and let my stomach rest. Also, I found trapped gas in the upper digestive system always started the AFIB.
I would force the burp but sometimes not enough, but a couple of days with not eating past my 7.00pm time and it has practically gone. I tried lots of supplements but I cut down on these and just not eating lots of different foods and only eating when your stomach signals (not your mind and the habits) it has saved me so far ( approx 3 weeks).
I think the foods produce gas that may push the diaphragm close to touching the Heart and so causing the AFIB ( my theory).