sometimes it starts and sometimes it does not....

I think there's a fault in the theft deterrent system. Get the vehicle to an auto electric shop or a Mazda or Ford specialist. If the problem's in the Generic Electronic Module (GEM) which controls many functions like dooorlocks, light systems, wipers, etc. then it needs to be addressed by a specialist. Here's a directory link for you: https://repairpal.com/mazda-repair-in-rockvale-tennessee