ProForm 730 intermittent power?

I've a ProForm 730 treadmill that will power up and work just fine but then sometimes (most of the time now) won't power up at all. Moving it around, turning it over (ugh) partially folding it, etc. sometimes will make it move again for awhile. This would seem to be an electrical short or equivalent somewhere but how to definitively diagnose where so that I can replace the offending part?