New poster here but went through similar, although not as severe symptoms with both a 2000 Toyota Corolla and 2000 ES300.
My suggestion would be to post up the codes you are receiving but barring that, locate and clean the MAF sensor which is located downstream of your Air filter box. Two small phillips screws is all it takes to remove the sensor. Unplug it and spray down the two small wires that are inside and at the base of the plastic column (hard to see) with electronic parts cleaner you can get at the auto parts store. They sell MAF sensor specific spray cleaner but I was unsure if that would harm the plastic on the Toyota/Lexus MAF sensor. Replace the sensor after it dries. Important, don't touch the platinum wires inside the sensor with anything.
Second, if you are receiving p1130, p1135, p1150 and/or p1155 codes, your A/F Sensors located on your exhaust manifolds are most likely bad and need to be replaced. Hope that if that is your problem, only the sensor on the front of the engine by the radiator is bad because the one in back against the firewall is a bear to get to and when I replaced mine, I stripped the threads and had to re-thread the hole in the manifold.
If the MAF sensor cleaning doesn't work, you may want to order one from RockAuto online and replace it. Easy DIY esp. if you already did the cleaning of the MAF and it didn't correct the problem.
Autozone or Advance will let you borrow a scanner for free to read the codes in their parking lot.
Good luck.