Is this a transmission issue or something else?

I have a 99 Honda Accord and it had a tuneup. However, after I got it back it had a new problem: Whenever I start my car firsts thing in the morning, it goes into gear (reverse or drive) but when I give it gas it still doesn't want to go. It coasts out of the parking spot. It seems like it has to warm up and then it drives just fine throughout the day. Some have told me it's the transmission, but it's not slipping gears. It just can't seem to get gas/umph to go.

I've been told to check my fuel filter. Would that help? I also had my transmission fluid changed and that didn't solve the issue.

Sometimes what also happens is I'll go to give it gas upon just starting it and the engine seems to die--but all the lights come on. It's like the engine is choked. Upon restarting it does fine (still coasting at first, though). But it is in gear. At least I think it is?

Replace the fuel filter and get the fuel pressure tested. Fuel pump could be on its last legs. Have the vacuum tested with a mevchanical gauge. The cat converter might be clogged up and need replacement.

"I have a 99 Honda Accord and it had a tuneup. However, after I got it back it had a new problem"

Seems pretty obvious that something happened to the car when the tune up was done. Why not take it back and complain? It sounds like something simple, possibly forgot to fasten the air intake hose after the service.

The transmission oil pump may be failing. A torque converter can also leak down over night if going bad. Let the car warm up for 5 minutes an see if it still happens.