Our fridgidaire gallery dryer squeals very loud for about the first 5 minutes of being on then quietly finishes it's job. It does this with each new load.

You could have a belt that is slipping on the heavy load of clothes when you first start the dryer, if so you may need to replace your belt.
Your problem sounds like drum rollers is in need of lubrication.
If you have a front loading machine, Unplug the dryer, remove the front of the dryer. This will expose the drum and belt, remove the drum and belt and this will expose the drum rollers.
Check your rollers for flat spots, if they have flat spots on them replace them.
If they don't then they probably only need lubrication. Lubricate the shaft of the rollers with a good grade of machine oil such as 3 in One oil. Reassemble the dryer, plug back in. This should solve your noise problem.
Good Luck,
I hope this helps