[BNaylor]

Does it occur at any specific rpm range? You may be getting chuggle or fishbite which is the torque convertor clutch (TCC) locking/unlocking. If it feels like a bad bog then the TCC may be stuck on.

You should get it scanned for any tranny DTC error codes using a trans capable scanner. Some do not trigger the SES light but are stored.

In the meantime check the condition of the ATF fluid and level. When was the last time the tranny was serviced? ATF and screen filter?

Finally, try this. Disconnect the battery negative cable overnight and then see what it does the next day.

Note: Before disconnecting battery make sure you have your security codes if Theftlock is active.