Compressor overloading

I have an emglo compressor I bought several years ago and it has worked flawlessly. But about a year ago it developed an issue. When it gets to 90 - 100 pounds pressure, the compressor starts overloading the motor to the point where the belt starts squealing. It seems there is something in the compressor that must is causing the resistance/overload. The problem is intermittent however, it does not do it all the time. It can do it one moment and then a few moments later be perfectly fine. If you can help me with this problem I would greatly appreciate it. Thanks