Phone keeps shutting down

Hello!

I have an iPhone 7 of a little more than 2 years, and in the past few months, it has started to randomly shut down. For example, today I had just started my music and then the screen just went black. The homebutton didn’t work either. So I held in the power button and then the apple logo came on - just like when you restart your phone. But when I turned it on it only had 10% left, and it was fully charged just a few seconds before. As this has happened a few times before, I just did the restart where you press both the sound- and power button. I had to do it twice before the battery went back to 100%. It shut down again later today too, but it lost 16% that time and they didn’t come back.

Everytime my phone does this, it only has 10% when I turn it on again, and I always need to restart it about two to three times before I get the percentage back. My batteryhealth also jumped from 78% to 76% just this week.

Is there anything causing my phone to shut down, and what can I do to stop it?