I'm going to say it will be similar to the experience prior to birth / conception, ie. we were nothing, and to nothing we shall return.

It's a scary feeling if you can grasp it. Grasping non-existence from within existence is difficult, I've consciously tried to do it and succeeded a couple of times, but it's fleeting and both times it affected my breathing and heart rate in a similar way to fear or panic or pain.

I think that once the power supply to my brain shuts down, that's likely the end of my conscious experience.

Dead brains don't feel