Hi there, lekkerbeardo!
Thanks for reaching out to the Apple Support Communities! It sounds like you are having issues with the Music app not opening properly and I am happy to help out! You've tried excellent steps so far restarting the phone and reinstalling the app, and 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 backup 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 phone up as new and test the phone to see if the issue is still going on. Then, follow this article to Restore your iPhone, iPad, or iPod touch from a backup
Let me know the results and have a great day!