Yeah this happens on my recordings pretty consistently actually. I've been messing around with EVP stuff for about a year and the static spike thing is almost like a warning that somethings coming. I use a basic digital voice recorder, nothing fancy, and you can see the waveform jump in Audacity right before anything intelligible shows up.
Not sure if its the device struggling to process whatever frequency is hitting it, or if its something environmental like EM interference. I lean towards the technical explanation tbh but then again the timing is too consistent to just brush off.
Anyone tried recording with two devices running simultaneously to see if the static shows up on both at the same time? That would help rule out whether its the recorder itself or something external. Been meaning to try it but havent got round to it yet.