let me look
when it shuts down when does it come back on and do you have to reset it, or does it just start back up?
Most likely the motor has thermal in the windings and is sensing worn bearings causing extra false load, the heat then shuts the machine down, some have to switch off and on, to reset some just start back up, [hate those a bimetal switch that moves with heat open, and closes as it cools so it starts with no warning]
most likely a combination of worn motor bearings, the time it takes to shut down should slowly get shorter and shorter,
If you are mechanical, pull the motor and you will be able to tell if the bearings are going, and you might see the leads to the thermal, you could jump it out, then it won't shut down, but sooner or later the root cause, bearings, wear in several parts, will get worse and tear it up bad, if it is a good one and you are not mechanical, take it to a vacuum shop and get an estimate, it should not be much to estimate it,
When it shuts off you have to turn it off and start it back up. I had thought about shorting out the thermal shutoff. It's not worth spending much on so will probably just do that and wait for it to wear out altogether. Just wanted make sure that was an option.