Help! Guys...Lady Needs Info!!

I own a 99 Chevy Tahoe 4-door LS with 110k and it's been pretty good to me, getting me from Florida to Calif. and then some. I've had some work done on the front end, Pitman and Idler, the rear trans seal replace due to leaking and the slip yoke lubed more than I care to mention..due to clunking on coming to a stop and taking foot off brake.
Now...something new: Intermittenly, I am getting a power surge, like a drain when I start the truck. New battery, about 2 months old, connectors spotless...engine is spotless...and it did it again tonight. I drove it today, no problem with starting. It's been sitting for about 4 hours and I had to start it to leave, it was a slow start, as though you have a failing battery. Could this be the alternator or?
Truck runs very good otherwise. Lots of power, no hesitation, no rough idle, no strange odors or smoke.
All gauges seem to be reading fine, but I noticed today that the battery gauge/alternator was running a bit low...like a drain.
Please help. Im out of work and do my own work on the truck other than major mechanical. I sure could use help..only vehicle I have.

Stop buy the local autoparts store that does free battery and charging system checks.Just because the battery is 2 months old does not mean its good.

Take a power meter and with the truck running see what kind of power the alternator is putting out. Then I would also disconnect the battery and hook up the power meter to that to make sure you get a good strong 12v.

I had a '99 4 door that had a similar problem. Turned out the battery cables corroded inside the insulation from the battery all the way to the fuse box and then corroded the terminal causing a short. Dealership had to replace the cables and put a new terminal in. This may or may not be the case for you, but just thought I'd give an idea.
Jeb

We replaced our cables also and everything went back to normal for now...