Won't crank, but only sometimes
 

Good evening all,

I have a 2007 LS with 107,000 miles. Normally, to start it, I put the key in, turn it straight to "start" and let go, and it starts without me holding it.

Late last week, I turned it to "start" like I always do, and nothing happened except for the "Check Engine" light coming on. I turned it to "off" and back to "start" and it started up no problem. When I put the key in and switched it to "on", everything lit up like normal, but when I tried to crank it, everything electronic would go dead, like I'd turned it back to off, except for "Check Engine". If I turned it back to "on" and tried starting it again, it would start just fine. It progressed so that I had to turn the key back to "off" before it would start. Just now, I went "off", to "on", to "start", to "on", to "start", to "off", etc, multiple times before it actually started. Took a good 30 seconds to get the engine to crank.

Everything seems fine in the on position before I try to start it. I haven't noticed any changes or inconsistencies in throttle response or anything else while driving it. It doesn't even have issues starting every time. I've had the issue both when it's been sitting for a couple hours, and when it was JUST running.

I switched relay #41 (Fuel pump) with #43 (high beams) with no change. High beams work fine with either relay, and the starting problem is consistent.

I'm not sure where to start, and work won't allow for me to take it to a shop until after the holidays, which is unsat as this is mine and my wife's only vehicle, and she's 8 months preggo. Can anyone give me some direction?