WIthout more information all anyone can do is guess.
That said, 180W for a power supply seems awfully weak considering that some video cards need 200-300W just by themselves. Running 2 monitors doesn't affect your power supply, though. At least, not directly.
Otherwise like everyone else said the problem could be hardware or software.
Hardware - Your system is overheating due to malfunctioning fans or something came loose, or excessive amounts of dust inside the computer. You'll have to open the computer to clean it out, check that the fans are still working, etc. Fans should be able to turn easily. If they don't or don't turn at all, replace them.
Software - Windows 10 will reboot your computer to install updates. Go into Windows Updater to change this behavior. Your Anti-Virus program may also cause reboots to install its own updates. Go into the settings of your antivirus program to change this behavior. Otherwise your computer may be encountering errors - check the Event Log for possible leads on that.