Loud noise from engine after starting.

I have a 2006 Tacoma TRD Sport 4x4 with the V6 and 238,000 miles. I went to crank up tonight with the outside temp about 55 degrees so not too cold and as soon as it started a terrible racket came from the engine. It almost sounded like a piston was hammering something. I turned it off immediately and then tried to crank again. It almost sounded like the engine had very little resistance from any kind of compression and took about 15 seconds to crank and ran kind of rough for about 5 seconds before clearing up. Any ideas what that was? This was the second time this has happened, it’s been probably 25,000 miles since the first incident. It’s running just fine now.

 

Need to get a video but from your description it sounds like timing chain slap or cam phaser knock until it gets oil pressure.
What's the condition of your engine oil? Do you have a check engine light on?