Even if it came very warm, I would not be contemplating full inspections yet! Leave them alone to get on with what they are getting on with!
A quick check for larvae is all that might be needed; feeding requires little invasion if that is the way you are going.
I am certainly not looking to be the first. Plenty of time for that later when the weather is altogether warmer. I do nothing which might hinder their build-up. Only if indications are of some malaise do I interfere.
The under-board would go in and any checking would be done in a couple of minutes or so, if possible. I certainly do not want any chilled brood, which is quite a possibility, as those are my next lot of brood bees. Losing 'one day worth' of brood probably puts them back far more than a week and quite likely more than a couple!
What would I be checking for on a First Inspection (when the weather is warm enough).
I can see from the outside that they are collecting pollen,
and by lifting the Hive that they have enough stores.
So they certainly appear happy enough at present