Transmission delay when switching to drive

[spoiler900]

Hello everybody! I have a 99 Limited 4X4 with 260,000 miles on the original engine and transmission. Over the past week, this has happened about 4 times and I have never seen this before. When I start my car and back out of my driveway and then stop to switch to drive, I let my foot off the brake pedal and normally before hitting the accelerator it naturally goes forward slightly like any car, but recently it would just sit there as if it was in neutral and then after about 4-5 seconds then a loud thud then I can finally go.

Im a college student and really really hope the transmission is not slowly going on its way out. It has only happened a few times intermittently but I am just concerned.

I am NOT mechanically inclined.

Advice or help please?

 

[Buckaroo]

First thing to check is ATF level.

Buckaroo

 

[Drcoffee]

Had the same problem with ours. A new battery fixed the problem. When its cold the battery is weaker and when you back up and then shift to D, the engine is at idle. So neither the battery nor alternator provide enough power to shift the tranny. Modern transmissions shift electronically these days.