iPhone 12 Performance Problems

Hi, I'm currently having massive performance problems on my iPhone 12.

It's about 14 months old and everything has been great up until now. Unlocking and swiping sometimes takes up to half a minute. The camera takes ages to open and shoot. I have the feeling that the screen sometimes runs at 20 hz and there is occasionally a noticeable input lag. My memory is not full, the software is up to date, I've tried reboots, it doesn't get too hot either, what can I do? Apps take soo much longer to start in comparison to my older iPad.

It's really frustrating.