The engine idles high at first and most times will not accelerate

On the first start, my car recently started idling high (usually around 1,500 RPMs at first) and most times won’t accelerate when I start trying to drive it.
Then if I shut the car off for a min and back on, sometimes it will go and once it gets going, it seems fine for the rest of the trip... Until next time I start it up.
Recently replaced the leaking engine valve cover gasket, and changed the spark plugs out for new ones.
I had disconnected the battery and performed an engine idle reset procedure which temporarily resolves the issue, but then it returns. Strange because once it gets going, it seems fine, but it’s severe lack of acceleration at first. Feels bogged down.
Recently brought it to Meineke to get diagnosed. I did the engine idle reset so I could drive it there... They kept it for 2 days and the mechanic called and said he drove it several times and it drove fine, and he had no problems so couldn’t diagnose.
No check engine light and not throwing codes...
Any help in diagnosing would be very much appreciated!