possessed pond pump?

i have a small waterfall with a pretty standard pond pump that's been active for the last couple of years. this year we cleaned it up and started the pump and all was well. for a day or so. now, something really goofy is happening. the pump keeps turning of and off intermittently. it runs for maybe a minute, turns off for a couple minutes, runs for a little while, etc. i haven't timed it or anything, but it seems reasonably periodic. what in the world could cause something like this? my first thought was a bad connection, but i find it hard to believe it would keeping doing this in a reasonably consistent pattern for three days... any thoughts? (the electrical connections are pretty inaccessible (by which i mean "underground" so i don't want to mess with them just to see if it helps.)

an intermittent problem is usually electrical, or heat... I think most pond pumps and fish tank pumps have a thermal protector in line, that will reset itself when it cools, and would explain your problems... especially if it seems to be keeping time; more erratic timing I'd look electric side.
Is it really pumping water? Is it a submersible pump?
the pump motor, if submersible, is water cooled and needs to be underwater...
the pump itself is watercooled, and needs water flow to cool