2000 gmc seirra will start fine first start of the day but idle rough and act like its going to die. Then it will come out of it and do it again. Any ideas?

Have the Throttle Body and the Idle Air Control Valve cleaned. Check air filter.

Where would the idle air control valve be?

Google your question with year , make, model and it will show you were and how to clean.

Thank u. Hope it works

Mine was doing that because I had a vacuum hose off and it was on a Yukon 2004 5.3 engine on the right side towards the firewall there's a hose that plugs in and it had a rough idle when I cranked it. It also had a wire that was loose in the wiring harness that hooks up to the throttle body. It would light up 'reduced engine power' and I had rough idle it would also cut off on me, so when the wire was fixed and the vacuum hose was put back on its been driving Perfect since.

Also I had the codes P2135 and P02I0 I believe that was popping up.