I will go with the thermal switch as well. You have described it rather well.
In addition to the bag there may be a secondary filter or two. And there are other issues too that could be overloading the motor and causing that.
You need to clean everything.
Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times