Something is loose...tighten things up...learn to use the cluster test to keep an eye on things...but this sounds like a loose/corroded connection...and I hope you get lucky and that's all it is.
Start at battery...alt...+ terminal...grounds
dmax on the radio--answering all your car questions as best I can!
watsonnwatson.com every Wednesday at 9 p.m. Call in! (661) 449-9340 Click "Watch and Chat"
Please 'friend' me!