If it does not happen in safe mode its an app causing it, so you would need to search for the culprit. Maybe you remember which was installed recently or updated?
Yvmuell also talked about updated apps and not only recently installed apps. Depending on your OS, there are ways to find last updated apps in the store.
The behaviour you described lets me think it is related to a camera app but I can be wrong.
I dont think so, especially as you still have warranty and that sounds a bit like a warranty case.
When you open a ticket with support , give them all the details yoj already tried, so they hopefully will not ask you to do the same again.