2000 Mazda 626 Mazda

The neutral safety switch is for the starter system. It prevents you from cranking the engine unless it's in park or neutral.

If the transmission doesn't work, the first thing to check is the fluid level and condition.

What do you mean by "the fluid was put back in"? What's the history leading up to this or the rest of the story? There's dozens of things that can happen to a transmission internally, but to work sometimes and not other times is almost always fluid level-related.

That still sounds like low fluid level. Was it checked with the engine running or off?

The only other explanation would be leaking seals in one of the clutch packs. Those times it does move you should likely notice other symptoms like sluggishness, slipping and engine speeding up, or a shudder when trying to move.

You need a proper diagnosis from a transmission specialty shop. You still didn't tell me if the fluid level was checked with the engine running or off so I'm not ruling low fluid out. If the cause of the problem isn't obvious to the experts, they'll perform some pressure tests to get a better idea of what's happening. I don't know how many miles are on the vehicle either or what kind of maintenance history it has had, so it's hard to know what will be needed.

Generally I'm in favor of repairing older vehicles rather than buying something newer, mainly because the newer a vehicle is, the more unnecessary, complicated, and unreliable computers it has and the more it will cost for repairs.

If I can't answer what? I asked you twice if the fluid level was checked with the engine running or stopped and you won't tell me. You really haven't provided any useful information, details, test results, or observations, so I did the best I could with nothing to go on. Sorry if you don't like the answers but that's why I suggested you consult a transmission shop.