Not cranking over

My Elantra would not start for my wife in 12/13 in 40 degrees for about 15 min and then started as usual. The car is in a lot across the city as it would not start in 8 degree weather, it had occurred earlier in the night, but once again started. I for some reason feel it has something to do with where the brake pedal is position (as like pressed hard to the floor). Called a battery garage and they said a battery should be ok on a 2012 and all lights, radio are fine. I will go now and it will most likely start with no problem. I want to run it by you first as I am unemployed, broke, and want to avoid the expense of dealer. Thanks