Could be a crankshaft sensor and a camshaft sensor issue...

Someone had a 1996 Lexus (Toyota) that would shut down suddenly, especially on hot days. It became intermittent on start up too. Turned out to be a crankshaft sensor and a camshaft sensor messing up the the ECM. No codes were ever detected.

(https://expeditionportal.com/forum/threads/engine-shut-off-while-driving.63599/)