Transmission going out

We have to start simple. First, if the check engine light is on, have the computer scanned. If it is not on, check the fluid to make sure it is clean and full. Keep in mind, if the plugs are bad and causing a misfire, the check engine light should be on. Check those two things and let me know what you find.

When was the last time it was given a tune up? Is the check engine light on? Even if it is not I would take it to a shop and have them scan it for codes in the engine and transmission controllers. There are a lot of codes that will not turn the light on or require multiple events over a set time period before the light comes on, one of those could give you more information to look at. In the mean time check the level and condition of the transmission fluid. You want to see it full and the fluid to be a nice red or light brown color. Black, gritty, burnt smelling oil is a bad sign and would likely mean a rebuild or replacement of the transmission.

Plugs, catalytic converter. All should have turned the check engine light on. Try scanning the system just to see if there is something stored.

Converter would not cause transmission slippage or jerking. Misfires would and a slipping clutch pack in the transmission could cause it as well as the loss of mileage. To check it you need to have a scan tool that can read the trans controller so you can see if the apply timing and rpm's as the transmission shifts are okay.

If that did the trick then I would consider doing a top cylinder cleaning as you likely have carbon build up at the injector tips as well. The cleaning would remove that mess.

That's good news. Let us know if it starts again.