2001 Nissan Sentra losing pickup

My car is a 2001 Nissan Sentra, and lately it’s been losing a lot of pickup when I step on the gas. This problem first appeared about three weeks ago, then disappeared after a single 15-min, drive, then came back yesterday and hasn’t gone away.

It’s really had a lot of problems since I bought it about 10 months ago. When I got it from the dealer, they hadn’t even bothered to clean it out and I found someone’s pills in the center console. Problems that might be related to the loss of “oompf” include that the coolant will be boiling when I take it up a steep hill, (It’s very rare that I’ll do this), and that I can’t find where to check the transmission fluid because it didn’t come with a manual.

Additionally, I just put oil in it a week ago. I live in American Samoa, where all driving is typically between 17-30 MPH and there is LOTS of rain. I really just need that bit of pickup for pulling out into traffic. I’m going to take it to the dealer (Good indie mechanics here are really rare and often unqualified) later this week to have it looked at and get the radiator flushed. Any thoughts?

Plugged cat? Just a thought. Any decent shop can check that with a low pressure guage.

Boiling coolant is a major concern. It may just be a bad radiator cap; or, it could be something worse (head gasket).
The loss of performance could be a plugged catalytic converter; or, it could be a dirty air filter, dirty fuel filter, weak fuel pressure, worn spark plugs.
A novice mechanic can take care of some of these things.