Weird electrical issue?

So I left my two dome lights on Friday night until around 1130a Saturday morning, all was well, the car started right up. Drove to work and back with no issues. Went to leave Sunday around 2p, the car unlocked and the instrument cluster came on like usual but when I went to start the car all lights shut off and no start. Got a jump went out for awhile Sunday evening with no problems.

Monday I go to leave for work around 11a with no issues, no issues leaving, stop at Pep boys to get wiper fluid and the car does the exact same thing when I went to leave. I was sitting in the car waiting for a jump then all lights come back on for a second but after I tried to crank the engine I got the same thing. Lights off and no start. Tried leaving this morning with all the same issues, took the battery to be tested after work and it's fully charged which tells me the battery is obviously fine as well as the alternator so I get home and hook the battery back up and the car fires right up :confused:

My guess was that maybe the connections were dirty but they were free of dirt and corrosion. I followed the positive wire to the starter which after running was pretty flimsy and warm. The other wire that runs under the fuse box was pretty stiff and cool to the touch.

Anyone have any ideas? I'm pretty dumb when it comes to electricity but maybe some kind of wiring?