Random voice on phone

At 5 am I heard my phone “rattle” and heard voices saying beer and sausage come from it.. My phone was on silent mode so I thought it must be something else but then it happened again and said something else. I took it off the charger and kept it by me to see if it would happen again. It didn’t. While browsing this morning the screen would flash like I was taking a screenshot occasionally. Eventually a notice popped up that said my phone was infected and that I should follow instructions on the screen... which I didn’t do. What’s going on?