There's not enough info here.
If the camera was idle, then it most likely hit the auto power-off time.
If the camera was recording video at the time, then it's very likely that the memory card can't keep up with the rate that the camera is trying to save frames of video.
The camera can shut down because of excessive heat (see page 215 of the manual where it describes the white bulb or red bulb icons to indicate internal temperature warnings.) Usually it would require more than just a few minutes for this to occur (unless you are shooting in a rather hot location and/or the camera has been used for some time already and not allowed enough time to cool off.)
The memory card issue is usually the #1 cause. I don't typically trust the labels on memory cards regarding their transfer speeds. I have never had one of these video recording shut-off issues... but then I only use top performing cards. If you want to shoot video, it doesn't pay to try to ecnomize on the cost of memory cards... get the best you buy. I typically use Sandisk Extreme Pro cards. Lexar's top cards also have a solid reputation.
I should re-emphasize... just because the label on the memory card claims it is fast enough... doesn't mean it's really fast enough. I suspect many of those labels exaggerate the performance realities of the cards and sometimes they are dishonest and report the "read" speed and neglect to truthfully report the "write" speed (writing is always much slower than reading.)
5D III, 5D IV, 60Da