It was the second time in three races in which Bottas has lost the lead of the race to his teammate Lewis Hamilton off the start.
The Finn pointed to an unusual feeling clutch as the reason why he was overtaken into turn one, but Mercedes isn't sure that is the explanation.
"We believe it was just a lack of grip on the pole position side," Mercedes sporting director Ron Meadows said in the team's Spanish Grand Prix debrief video.
"If you look at the support races, more often than not the second position guy or even third or fourth had a better start than the pole guy."
Trackside engineering director, Andrew Shovlin did however say the team would be thoroughly investigating the car back at the factory to understand if there was indeed any issues relating to the clutch.
"That's one of the elements. You get a bit of wheelspin and then the wheels are slipping, the clutch is slipping, there's a bit of an interaction.
“We're going to get all the bits and have a good look at them anyway this week to understand it. At the moment we think the number one issue is with the grip and not an issue with the car."