I have a 2014 Nissan Altima, having an issue where I am parked for a little bit but sitting in the car. The car is off but I will turn the accessories on (radio, interior lights, sometimes exterior lights, A/C, phone charger, etc) for maybe 20 minutes and when I go to start my car again it struggles really hard to turn back on. It is almost as if the battery is turning over and it finally musters up the ability to crank after 3-5 seconds of audible struggling compared to the usual 1 second seamless crank. However, I have a brand new battery not even a year old, and when I went to get my new battery I had them test the rest of the electrical system and was told everything was fine. I am just concerned because of how bad it struggles to turn back on after running accessories for ~20 minutes, when I have been told that cars should be able to run just accessories for hours without issues.
Extra note: My high beam headlights have started occasionally flickering for less than a second. It does not happen often at all and seems to be random, however I am including this anyways in case it could be tied to any other electrical issues.