Toyota Repair: 1996 Toyota Camry 4 cyl. cold start, toyota camry, oxygen level

Question
My Car has been at the Toyota repair off and on since early Dec.  When I would start the car the first time , it struggled to get into gear and start moving. It would just creep along.  Then it would go into gear.  All diagnostic testsf4g$h proved, no problem.  Some mechanic told my son in Denver who has had a similar problem that the Oxygen level in the gas is higher now than when our cars were built.  Ideas?

Answer
No I don't buy that explanation, I'm not sure what is going on with your camry, it may be a transmission problem but I don't have enough information to be sure, does the engine rpm go up but the car not move or move real slow until it goes into gear? Has anyone checked the transmission fluid level?