Driving along highway and felt engine rev up slightly like transmission put in neutral …laid off gas for a second and gently reapplied and seemed fine. Came to stoplight and took off and 3 seconds later came out again and would not move . No pop or sound . Reverse / low / 4wd /2wd tried all no difference . Confirmed fluid is full . No issues before , shifts great . 265k miles . Towed to local shop who is backed up for weeks before they can look at . Any thoughts on what might have caused ? I’ve had transmissions go out on other cars but always had issues before that told you it was going to go . Wondering if some linkage / other easy aspect I can look at . Appreciate any insight !