So when i started my HS today i heard a loud rattling sound from under the engine, like it was knocking against something. Looked under the car and there was nothing out of the ordinary / the plastic engine cover panels seemed secure. After startup, all sounded fine and the drive was uneventful. Any ideas? Car is garage kept and it was 70 outside, so not too hot or cold. Car gets ~35.5 mpg as it has for years so seems to be running fine.

 

How is your oil level? How many miles are on the oil? Maybe like the 2GR-FE V6 this 4 cylinder motor develops a death rattle at start up as it ages.
You may want to view the Camry hybrid forums at Toyota Nation as they get a lot more traffic and it has the same engine for similar model years.

 

yeah good thought, but I just checked and my oil level is completely full, with about 2800 miles on this batch. 134K total on the engine. I did find a few fasteners missing from the plastic shrouds above and below the engine, so maybe it's just those things rattling on a rough start? I need to chat with my dealer as they are the only ones that have serviced my car. I started the engine with the hood up and no rattle - seemed pretty smooth.