My Hotpoint minstral FF keeps shutting off then kicks back in?

I have had this problem for some weeks, the fridge freezer cuts out (panel still shows temp) The fridge goes to around +8 and the freezer to -2 then it kicks back in. when it gets to +6 and - 15 it then stops agian. I took off the panel at the bottom, there was lots of dirt and it seemed to be Ok after that for a while but now I have the same problem.

The firdge light does not work either, not sure this is connected?

When I power the fridge up the panel shows P1 for a few seconds before the temp is shown?

Could anybody help?