Why is my Dremel losing power and eventually dying?

I've had my Dremel for 4 years so maybe it's just wear and tear. But when I use it, it sounds like it starts to lose power, almost like I'm turning it on and off really fast and lowering the power intensity, live revving the engine of a car. Eventually it just dies. There's also small sparks that can be seen inside the motor.

If I leave it alone for a while, it works again just fine for a couple of minutes but then it does it again. Is this fixable? Obviously I don't want to use it anymore but I also want to know if I can fix it before buying another one or if buying a new one is more affordable. Thanks in advance.