I have experienced reboot 2 times today while adding roms and snaps etc just random rpi3 cpu temp 104
Are you getting the rainbow square in the upper right corner of the screen?
Do you have a heatsink?
What resolution are you running at?
I've been running the collage screensaver on my RPI3 all night long without issues.
I'm using the video's the screen scraper of AM downloads also.
Can you post a copy of your config.txt from the boot directory?
If your RPI 3 is overheating it should have configs for throttling down the CPU in the config file.
also, have you updated the firmware on your RPI?