2008 LEXUS LS460 Power Train Problems

THIS HAS HAPPENED OVER 5 TIMES SINCE OWNING THE VEHICLE. AFTER OIL CHANGES AND OFF/ON THROUGHOUT OWNING THE CAR IT WILL HAVE A HESITATION ON THE ACCELERATION. IT WILL HAVE HIGH RPM'S, BUT IT IS NOT GOING ANYWHERE (LOUD ENGINE NOISE). THIS IS VERY DANGEROUS IF IT DECIDES TO DO THIS WHEN PASSING SOMEONE ON THE HIGHWAY AND THIS MORNING IT DID IT WHILE PULLING OUT INTO TRAFFIC AND ALMOST GOT HIT AS THE VEHICLE DID NOT MOVE. *TR

I HAVE 30,000 MILES LEXUS 460 - VEHICLE DOES NOT ALWAYS ACCELERATE PROPERLY. LOSES POWER AND WILL NOT KICK UP FOR A FEW SECONDS UNTIL FINALLY KICK UP. THIS HAS HAPPENED AT LEAST 5 TIMES IN 3 MONTHS. NOT SAFE WHEN YOU COUNT ON THE CAR TO SPEED UP TO GET INTO THE FREEWAY OR INTO A STREET WITH TRAFFIC. NO ACCIDENTS SO FAR BUT I AM AFRAID THAT WHEN THE POWER IS NEEDED IT WILL NOT BE THERE. CLOSE ACCIDENT IN THE FREEWAY AS THE CAR FAILED TO SPEED UP WHEN GETTING INTO THE FAST LANE. MOST OF THE TIMES THE ISSUE HAS BEEN AROUND 20MPH AND NEEDED TO RAMP TO GET INTO THE FLOW OF TRAFFIC. I AM NOT SURE WHAT GEARS ARE INVOLVED BETWEEN 20 MPH - 40 MPG BUT THAT IS A CRITICAL SPEED TO FAIL - IT WILL CAUSE AN ACCIDENT IF CONTINUES. *TR