Is this the likely reason?
Should I unscrew the back of it & get the dust out?
Swtch off and unplug from wall
Take the screws out the back and slide back the side cover (left).
you can suck out the dust with a vacuum cleaner but do not get the hose too close to the components or use a hair dryer on cool to blow the dust out.
If the fans are caked you can scrape the fan blades with cocktail stick or those wooden sticks women use for their fingernails (not nail file board)