1998 cadillac concours won't start

Hi, I am new here & need some advice please. I own a 98 caddy concours that only has 53000 miles on it.The last three days we have had bitter cold weather & when I would go out in the mornings to start the car the last three days it started fine but I would hear an electrical pop sound. Well I would take my daughter to school 2 days & car ran fine & when I got back out in a 2-4 hours(she only had half days this week) it started fine & there was no pop sound. This morning I had to run to the pharmacy & same deal at start up with the pop sound & I was inside maybe 10 minutes. When I came right back out & turned the key the engine done nothing, the only things that happened was the trunk popped open, the disc in the cd player popped out, clock came on, gas cap cover opened & service engine soon light flickered real fast & only heard a clicking sound. tried three times no luck.I am disabled so I had to get a ride home & leave the car. This car has ran perfect always & taken care of as far as premium 93 or higher Sunoco in it & oil changed on time. If it may matter I had let the gas run down almost on the E.Thank you in advance for any help.Rosco

My friend took me to the car & it started easy with a jump from his truck. Took it to auto store & battery was at 12.6 volts to start but soon as he put a load on it it took a serious drop. But the final analysis said recharge & recheck, not that it was bad, but it is the original battery so I am gonna try a new one instead of recharging as no car should have an 11 year old battery, something I forgot about in the upkeep & go from there.

If anyone still has an idea of what is going on it is appreciated if you would like to post. Thanks, Rosco

Make sure the battery cables are clean especially the ground side.