Every time I turn on my ac it will automaticaly turn off after several minutes and then "fr" code is blinking to the monitor, and then I need to unplug the unit to turn it on again.

It would help if you told us what brand and model your A/C is. As trouble codes are not standardized.

Without the brand and model number we cannot know what the code means, but if it's dirty and really clogged up with dirt it will not run if it has freeze protection which most all new units have. "FR" on most models means it needs cleaning or the fan is not blowing. I bet you need to remove it, take it outside and wash out with water and Easy-Off oven cleaner applied to coils. Get the really caustic kind that has sodium or potassium hydroxide and foams. Wear gloves and remove the cover so you can see both sides of the coils, especially the inside coils. Wash it out well and then turn it on its side and wash out even more to get it totally clean, like new. Make sure to flush out the drain, too. Reassemble and it will be fine. That's about the only maintenance you need to do to a window unit each year. You can also go to an HVAC parts store and buy an alkaline coil cleaner that has sodium hydroxide (liquid lye) as its main ingredient. Make sure to wear thick rubber gloves, a face shield, and a good dust mask. This is very, very important as the built up molds and bacteria can kill you when sprayed with water so it goes in the air. Be upwind of unit as you wash it out, if possible, too.