Screen freeze, big pink pixels on my screen, then restart by itself

Good day!

I just encountered an issue with my IP 12 Pro. While I was scrolling through my phone, my screen suddenly freeze and it show many pink squares (looks like pixels but a bit bigger). After few seconds, my phone restarted itself. Does anybody know why it happen and how to prevent it from happening again? Please kindly help, I just bought this phone 3 months ago, I am planning on using it for 5 years. I hope that this wont be a huge problem for my phone longevity. Thank you!