Warping of bottom of print
Photo Credit: Courtesy of 3DStockPhoto ( image)

If you have a heat bed, heat it up accordingly (for example for PLA 50°C first layers, 40°C then can be a good starting point).

If the first layer isn't close enough, then warping can happen (Happened to me when moving from 0.3mm layers to 0.1mm).

If you are under extruding / have dirt in the system (the heat chamber) so that extrusion is uneven it can make warps.

And as always, you can try to print slower, it helps not always but often.

Please also do tell what temperatures (heat bed & nozzle) you are using and what material.

HTH