Hello. I Was Driving After An Hour Or So On

Hello. I was driving after an hour or so on a high speed highway when I lost conciousnous for a few seconds. I awoke to find I drifted a few feet to the left which took my car into the next lane. No one there so no collision. This occurred a couple of more times over the next half hour or so. I pulled over and rested. I resumed my journey after a 20 minute break and after a coffee with cream and sugar. End of problem. I'm on several medications for cholesterol, high blood pressure, Barrett's disease, beta blocker and blood thinner. I had an AFib attack about a year ago. My doctors tell me everything is under control. Any idea what might have caused the momentary blackouts? Thank you.