iPhone13 with ios 17.1.2

I had the same problem until I realized my finger was resting on the right side button while I pressed volume up or down. It's easy to hold your finger there but once I took care regarding my finger placement, the problem stopped. The iPhone was just following the instructions I did not realize I was giving. Holding the side button/Up volumes is how to take a screen shot. Holding that side button/volume down turns the phone off.

Do you have a case on the iPhone? It would seem that something is pressing the power button on the side of the phone. If you do have a case on the phone, try removing it and testing to see if you experience the same behavior.

Carol B got where I was going. The way to take a screenshot is with the volume up and power button together, and if you press and hold the volume button and the power button together it will bring you to the shutdown screen. Hope you got it all straightened out.

You are very welcome, AscosiL.