Hi mj, welcome to our little corner of the 'net.
Have you cleaned your router lately? Sometimes they get plugged with sawdust, and no air can get thru for cooling purposes. There is a thermal shutdown due to heat, after a cool down period it resets itself. Try blowing it out to see if it makes a difference. If your router has seen lots of use, the brushes might be worn enough to require replacement, or a bearing might be going bad, (normally the bottom one) and siezing due to heat.
Sometimes I wonder whether the world is being run by smart people who are putting us on
or by imbeciles who really mean it.