well it finally happened, engine sound like loose bolts in a can

Welcome to the "Hammer/Club".......

 

Welcome aboard and enjoy the noise. Be sure to report it to your dealer and/or Toyota care.

 

What can it be?

 

Water which had condensed in the intake manifold after an incomplete warmup cycle in [un]favorable atmospheric conditions, and which gets sucked into the cylinders during the next start-up. So they say. A back-yard way to blow out the carbon in your 50's junker [or blow out a rod, a head-gasket, etc...].

 

^^ Aye. To reduce the chance of this occurring simply allow the engine to complete the first stage of the warm up cycle before turning it off. I.e. do not start the car, back it out of the garage and then immediately turn it off. Allow the engine to turn itself off before shutting the car down.

If you need to move the car a very short distance it is better to push the power button and immediately put the car in EV Mode. Move the car and then shut it off without the engine starting.

 

^ And if EV's not available, which is often the case, you've got the 15 seconds or so of mandatory EV, if you move fast you might dodge engine start up.