Battery gauge fluctuates when driving, then battery light and check hybrid system warning come on?

The battery gauge fluctuates up and down while I drive from between the 1/4 marker on the low side up to the 3/4th on the high side. When the gauge gets up to 3/4, I've had issues with where the car will start to drive on its own. It used to only happen when I was driving on the highway at 55 MHP or above, so when the issue happened, the car would just start self-driving at whatever speed it was going and then the battery light would come on, the Check Hybrid system light would come on. The AC would not be cold anymore, and I would pull over to the side of the road and turn the car off, turn it back on, and then I was able to drive it again. The first time it happened I was using cruise control. But the 8 or so times it has happened since I was not using cruise control and now the problem sometimes happens on city streets, not only on the highway. I've seen other people say they get a message to "Check hybrid system - stop driving car." Mine doesn't say that, it just says Check Hybrid System and the red battery and check engine light come on. But once I turn my car off and turn it back on, I'm able to drive again like usual. I don't know if it's an alternator issue or a battery issue, or a fuse issue or some sort of cruise control sensor problem. Any help would be greatly appreciated.