Which model of the a series are you using @zimma71
Have you tried any troubleshooting advice such as Safe Mode which disables downloaded apps , themes and 3rdcparty launchers https://www.samsung.com/uk/support/mobile-devices/how-to-start-my-galaxy-device-in-safe-mode/ or clearing your phones system cache files.
Clear your System File Cache via the instructions in the Samsung Link. You may need to hook upto a computer or insert your headphones to get to the recovery menu. https://www.samsung.com/uk/support/mobile-devices/how-do-i-clear-the-cache-on-my-device/
Check everything is updated in regards to your software and apps and if absolutely necessary back up and factory reset.
Finally a Samsung Experience Store / Samsung Service Centre can take a look at the phone.
Daily Driver > Samsung Galaxy s²³ Ultra 512Gb in Phantom Black.The advice I offer is my own and does not represent Samsung’s position. I'm here to help. " This is the way. "