Fake alarm

Thanks for getting back to us, kristiānsfromsalaspils!
At this point, it would be a good idea to be sure there is not a software issue as the root cause of this for you.

• Check out this article for the steps for How to back up your iPhone, iPad, and iPod touch.
• Use this article for the steps to Use iTunes on your Mac or PC to restore your iPhone, iPad, or iPod to factory settings.
• Once that is done, set the device up as new and test to see if the issue is still going on. Then, follow this article to Restore your iPhone, iPad, or iPod touch from a backup

Hi there, kristiānsfromsalaspils!
Thanks for reaching out to the Apple Support Communities! It sounds like you are having an issue with an alarm going off that is not showing in your alarms in the Clock app and I’m happy to help! First, in the Clock app, tap Bedtime and be sure there is not an alarm turned on there.
If there is not a Bedtime/Wake alarm set up or the issues remains, I recommend checking out this article with steps for How to force an app to close on your iPhone, iPad, or iPod touch and quit the Clock app. Once it’s closed, Restart your iPhone, iPad, or iPod touch and test to see if the issue is still going on.
Let me know the results and take care!