This has just happened today. It started after I manually restarted my computer (shut down, and then after a few seconds power up). The first thing that happened was that for some reason, steam wanted me to download Terraria again, which was very odd because after checking preexisting files, it didn't download anything: it only used a few bytes for the "download". After that, I opened Terraria via my desktop shortcut. Since I usually have Task Manager open I saw nothing wrong with how...
Terraria makes my PC "restart"
Terraria makes my PC "restart"