How exactly does convection motion start?

[erobz]

I’m kinda waiting for a scientific explanation for this
At low temperature (below 65 Celsius), and on an inclined plane, especially considering the butter from the center of the pan which presents movement in both directions, i.e., up when closer to the heat and down when further away from it.
As it was mentioned earlier, the butter should just melt and flow downwards, but what happens is a distinct motion whether closer or further from the hotter region.
Also the Marangoni effect should facilitate the movement away from the hotter region, so what mechanism is driving this motion here?
Is it capillary?

You aren't going to find one other than melted liquid butter is accumulating in the pan. It flows to the lowest point in the pan...which is that deep channel around the perimeter. The liquid butter fills (partially) the channel(s) that are blatantly present in your experimental setups.

Change nothing about the pan setup, remove the heat and butter, just leave the pan as is. Now drip colored water in the pan. What do you observe as you drip it in?

 

[Dale]

As it was mentioned earlier, the butter should just melt and flow downwards

What was mentioned earlier was that the solid pat of butter should slide downhill.

There are many reasons that the liquid could flow uphill: surface tension, convection, increased volume, etc. There are also many reasons that the liquid could appear to flow uphill when it isn’t: camera angle, non-flat bottom, flow down pat, etc.

Nobody can identify the actual factors but you. That is why we are not discussing your kitchen experiments. If you wish to discuss this effect then find a scientific source we can discuss.