This is from the Dyson web page:
Get expert help Thermal cut out Most Dyson vacuums have a built in safety system that stops the machine if it begins to overheat. This usually happens because the filter needs washing or your machine is blocked. If your machine turns off on its own, unplug it and leave it for at least an hour to cool down. Remember to check the filter and look for blockages before re-starting.
Any non- domestic use may adversely affect the filter performance such as vacuuming up plaster dust.


Sounds like your vacuum is overheating. Check the above.


Lou