Sometimes when I take the phone out of my pocket I have to enter the PIN code again, just like if the phone has restarted, but I don't have to use the password to get into it afterwards.
Then I have a problem where I can randomly get an error saying it can't find the SIM card.
I've replaced it and it was fine for about 1-1.5 months before it started again.
I've now changed the location of the card so we'll see if it gets better.
I bought the phone (a Samsung Galaxy A35) at the end of May so I don't think it should be messing around this much already.