Dash and flasher lights flash on and off

On my 2000 Tacoma, auto trans, six cyl, when I first start my truck, the front and rear turn signal lights and my dash lights flash on and off for about 20 seconds, then everything goes normal.......any idea why or where to start trouble shooting

 

Mine did this as well for a while, do you have an aftermarket alarm installed? I did and one day dropped the remote in a cup of water and ever since the remote was shot my truck would do this but if you turn the the trucks parking lights on the lights quit flashing and you just hear a clicking noise?
Eventually I got under the dash and just tore out the aftermarket alarm box and it cured everything. Hope it helps, also I bought my truck with the alarm so if your a second owner then that's a possibility!

 

Chad, thanks so much for your help, I disconnected the aftermarket alarm system and my problem went away.

 

Good to hear, glad it worked out for you!