Definitely that would be the number 1 thing to look at. But sugary oatmeal as the solution? Or was that just a coincidence and it went away by itself?
My guess (big guess) is that the condition isn’t caused my ketosis. It’s always there but was exposed by ketosis. Being is a sugar-addled food coma covers it up since you don’t wake up, but the underlying problem is there… you just sleep through it and unconsciously move enough to reset.
The only way to tell is to go to a sleep clinic. Get some real data.
You might need to go to a sleep specialist and have a sleep study done.
What may be happening here is that, on Keto, you were not reaching deeper sleep states before a blockage (i.e. your throat simply closing) occurred so, you woke up and realized you were not breathing.
With some carbs you may be reaching deeper sleep states but, the blockages might still be occurring - you just do not wake to notice them (a sleeping partner sometimes will notice). Even if you feel you have good sleep (because you don’t notice the breaks in breathing), breaks could still be happening. If this is the case, it puts an unnecessary stress on your heart and shortens your life.