I have an electric fan. That starts slow. The blades go around at
A snail's pace. After a few minutes it goes to full speed. Someone told
Me it's a capacitor that is wearing out, and can be replaced.
Is this true? It's a multi speed cheap fan. I used WD40. And runs okay
For hours. It just at startup, it takes a while to get going.

I'll assume a simple portable electric fan. I'd guess that the bearings are cruddy. Rotate the fan by hand after it's been off for a while, then after it gets to full speed and running for a while try to rotate the blades again. The resistance should be the same. Be sure to unplug the fan before sticking fingers in it. WD-40 may help clean the bearings. Then oil with sewing machine oil.

I am assuming this fan is a single phase fan. Single phase motors have two windings. A start and a run winding. When the fan first starts, it uses both windings. When the motor gets to a certain speed, a switch (Called a centrifical switch) takes the start winding out of the circuit and it uses only the "run" winding to continue running. It almost sound like you have lost one of the windings in the motor, which is common. A decent electrician can determine through measuring the resistance of the windings if one of them are gone. Also, of course check the stiffness of the shaft to see if it actually is a bearing problem. Understand that if the bearings are keeping the shaft from turning, it can cause the burnout of windings. Make sure you figure out the root cause, not reactionary causes.

I'll assume a simple portable electric fan. I'd guess that the bearings are cruddy. Rotate the fan by hand after it's been off for a while, then after it gets to full speed and running for a while try to rotate the blades again. The resistance should be the same. Be sure to unplug the fan before sticking fingers in it. WD-40 may help clean the bearings. Then oil with sewing machine oil.
I had exactly this problem - lubricating just the front bearing solved it (the rear bearing is less accessible)