Randomly restarting phone during normal usage

Hi everyone,

I would like to advise you how to solve the problem of randomly restarting the phone.

I bought the phone after the premiere in the German Mediamarkt and initially the phone worked fine, but over time problems started like:

- apps do not load and immediately crash to the home screen, sometimes freezing the phone

- applications stop working while using them and sometimes cause the phone screen to turn off and the only way to wake up the phone is to press the power button and wait for the phone to reboot

- And the worst thing, namely the phone at random times displays the word "Google" and starts booting like it was restarted manually, I've been watching this phenomenon for a year and I can't tell if any specific thing provokes this phenomenon. Sometimes it happens when the phone is playing music, sometimes when I use navigation, play games, browse the Internet and it happens even when the phone is on the desk and all I see is the screen is lit up and shows the Google logo.

Unfortunately, I live in Poland and the Google guarantee does not work, and the store where I bought the phone does not respond to my e-mails and I do not want to organize a trip to Germany just to make a complain

So maybe someone have similar situation and know how to repair it or only thing is to complaint it?