The weird issue...about a year ago 30 min into a highway drive the D (Drive) light indicator on the dash between the RPM and speedometer flashed. It was quick - wasn't even sure it happened, but in the time since then it has happened a lot at both highway and city speeds and sometimes it stays off for 5 seconds or so. Some drives it doesn't happen at all - sometimes it is a lot - sometimes it is a few times at the start and doesn't happen again even for a long 5 hours drive. There has never been any warning lights - AT or Engine. The speed remains constant highway or town streets. The cruise control works and doesn't hick up when it happens.

Thanks

 

Welcome to the forum.

You need to have your Mazda checked for any and all codes, pending codes and the monitors to star with?
Just because you do not have an engine check light does not mean you don't have issues reporting to the ECU..
At least some of the things described you should have gotten an engine check light!

 

I did have it put on at a mechanics shop and he said there are no codes and I will need to let it get worse.

 

He did not check it correctly if that is what he told you. Plain and simple.
I would guess he looked only at current DTC and nothing else? As I said with what you posted your monitors at least would show not in readiness and I am sure there are pending DTC(s).
Find a service technical that actually knows how to look at the ECU registered information!