After I changed the

car (not key fob) battery, the car now remotely starts when I hit the

lock button on key fob AND when locking w/ door handle lock button from

inside car. The car only runs for a couple seconds and then turns off.

I've tried disconnecting the car battery for an hour to reset things,

but no change. I bought the car used and it was *not* equipped with

remote start function, as far as I know (?).

Has anyone else seen or heard about this??

 

Some CX-5's, including the 2018, come with remote start.
Pressing the lock button quickly 3x will start the vehicle on some FOBs.
You will need to go online to find out which FOB you have.
Keep in mind that buying used there is no guarantee it is the original.
You may need to reset the FOB.
First replace the battery then hold the lock and unlock buttons on the fob simultaneously for at least a minute. This will reset the system. The interior lights should flash.