PS5 blinking grey dots

Recently bought a ps5 from someone on offer up had it about a month ps5 was running great it still runs great but today when I was playing a game there were blinking grey dots that I noticed that weren’t there before I’m wondering is this a GPU issue? I rebuilt database and moved my hdmi around the grey dots have disappeared but dont know if they’ll eventually come back, was wondering if I could send my PS5 in to you guys?

PS I dont have warranty so the only thing i can do is send it in for repair would love some help, thank you.