2002 Ford Explorer Electrical Problem?

While driving down the road ALL my guages will spike clear up and all the lights on the dashboard will come on for about 3-5 secs then everything will bottom to zero for about 3-5 secs then go back up to where they are suppose to be. My radio will also go off and come back on in this process but not my radar detector I have plugged into the cig lighter. This is random wjen it happens and Im not doing nothing in particular just usually driving down the road. Engine works fine when it happens. I just replaced the battery 1 week ago and had the alternator checked, which was perfect. Every now and then the guages will do all that then stick, for example saying im going 60 mph, odometer wont work, temperature outside dont register, even when Im at a complete stop. Then I turn the engine off and it all still is stuck and the radio wont go off and clock stays on till this drains my battery. Now it only does that maybe ever 4 days but as for the guages spiking and dropping every now and then it usually happens everyday after driving the car for about 30-40mins. It may do it then not do it again for about 15 mins later or it may do it then do it again 1 min later and it doesnt matter what Im doing it happens. I tried seeing if it was when I turned on the lights or radio or stepped on the brakes or whatever but no its like it has a mind of its own and does it whenever it wants. Someone said maybe the ignition switch, alternator, or GEM. I have had it to a shop but they say they cant help me till the problem actually happens and they see it well, lol, how in the heck do I know when it will happen and like I said before it only last for25 secs or so unless it sticks. This is my only car so I have been driving it still and someone said to stop cause it will catch on fire from the problem! Please help! Thanks