Its possible your coil is starting to go. When they do they start to draw more amps. You can test it with a multi-meter by doing a OHMs reading on it. The closer it is to continuity or less than 1 the closer it is to failing. Unfortunately I don't what the spec should be. From my experience based on an AC clutch maybe 7-15 ohms?
Actually here is a pretty good walk thru. They state 3-5ohms is acceptable for an AC clutch, I'd say our PTO clutch is probably more heavy duty so would vary.