That an interesting / odd waveform (which is a way of admitting I don't know the answer). Two possible guesses, the first is a loose connection from the clamp to the BNC connector on the PicoScope causing the signal to drop out - check turned / not loose. The second would be a loose connection on the vehicle - perhaps battery terminal.
Can you recapture but add channel B as battery voltage and then post again - I want to see if the battery voltage jumps up a bit when the current drops out. Best to post the screenshot as you have an the .psdata file for this one.
I thought i would jump on this post(hope you dont mind) as i am experiancing a similar problem, just purchased a pico advanced auto kit, i get the same thing on a battery test or comp test, have the same issue in pico scope software even connected to a battery sitting on the floor totally away from a vehicle i get erratic waveform. I have tried differant laptops, test leads and software versions. only thing i haven't subtitued is the pico(for obvious reasons). Does the pico team have any advice on this? i have been in contact with my supplier in australia and they currently dont have an answer