MacBook Pro 17" crashing and restarting

My Early 2011 17" MacBook Pro, 2.3GHz Intel Core i7, 1TB SSD, 8GB DDR3, OS High Sierra 10.13.5, has started to crash and restart continuously and spontaneously.

The screen image can fragment on start up and turns blue and/or grey but can recover to a normal state .

I ran the extended Apple Hardware Test and it twice came up with Error Code 4MEM/66/40000000:0x84cfa818.

It then says I should contact Apple Support but Apple do not support my Mac model as they regard it as redundant.

Does anyone know what the error refers to?

I would like to have some idea before I attempt to get it repaired.

Thanks, Brian