Insane lag iphone 11

Hey everybody today i was on my phone and suddenly a black screen appeared with a charging logo and my phone stayed like that for a few seconds but when it pops out my phone was in the home screen page locked of course i can unlock it but Is it normal because i read that if reboots itself and the battery usage is way less powerful than before it can be a spying app . Also my phone battery really significantly has gone down. Of course i checked that and how to make sur that you’re not being spiyed. I just did the last apple update. Please just tell me if im worried for nothing or it is normal or not .