Huawei p8 restarts uncontrollably, what to do?

Sometimes the phone starts "new", which means I make something wrong that comes the vodafone start screen and that is a few seconds then and then I'm in the lock screen and can continue… But must not enter any password or other new. Did not do anything at all was not even on the phone and it still starts "new"… Can anyone help me, I have mistyped in the settings? Or so?

This is normal after 3-4 years.

Save your data and then reset the phone to factory settings, this goes through the settings at Backup + Reset, but then you need your Google credentials if you have set Google backup and restore on, you do not know that then off put.