erratic idle at times

[benztech82]

Hi guys. I'm new to this forum but have been posting in impala and Mercedes
categories. I'm having a little trouble from my 2003 Tahoe 5.3 75k. only in the summer when temps stay up in the mornings (70-75 deg F) the truck will
occasionally develop an erratic idle. it will bounce from regular idle speed which I think is about 700 rpm (I don't usually drive it) to about 900 rpm at
about 1 sec intervals or shorter. This will occur for about 30 seconds and slowly clear up and it will not happen again until sitting overnight and completely cooling down. IMHO it sounds like the fuel pressure is leaking down but I may be wrong. I was just curious if this is a common problem or do I need to do some digging and testing. just trying to skip a few steps if possible. thanks in advance for any help or advice offered.