I had an HP notebook with a battery that went bad. Even when the notebook was plugged into AC power, the battery still made the computer fail to function.
My issues started like yours, then the PC just failed to function altogether.
Try removing the battery and running just by AC power. If this fixes your issue, you need a new battery.
My notebook continues to work this way to this day. I still don't feel the $120 to replace the battery on my 5 year-old laptop is a fair price, so I continue to only use this PC plugged in.