[MagicRat]

I think you have a simple electrical supply problem.

Have you moved this compressor to a new location, or use different wiring for it, such as an extension cord?

Compressors need thick wires to let it run properly, like 10 gauge or 12 gauge. Also, avoid long extension cords and wires. The shorter the wire, the better.

If you use a thin extension cord, (ie 14 or 16 gauge) and especially a long extension cord, the motor will behave as you describe.

Also, is this a 220 volt compressor? If yes, are you using a 220 volt outlet, or a 110 volt outlet? 220 volt would be required if that's what its designed for.