Screen flashes, sometimes red, sometimes just flickering

So sometimes after waking my Mac from a nap, the screen will briefly flash red before allowing me to sign back in, or it will flicker. Usually the screen will flash red, but more recently it began to flicker and after I signed in, the screen continued flickering. I shut it off and tried to reset the PRAM because I heard that typically helps (?), and since doing that, the screen hasn't flicked. I thought all was good, but then a few days ago my screen flashed red this time. I like to think that this doesn't happen every day, but it certainly happens enough for me to be really very super concerned.

I don't know what's wrong with my laptop or what to do, so any advice would be nice. My laptop is completely functional after it flashes red, but it's still kinda scary - even scarier when the screen just blinks and flickers. I'd like to get the problem fixed if I can to prevent problems in the future. I have the MacBook Pro 15.4", and it was given to me by my college in 2017. Please send help!