Objects disappearing randomly, any ideas??

Hi I am fairly new to Blender so this may be a very simple problem but I am finding my models become weirdly invisible at times and am not sure how to rectify this… I’ve added some pictures to illustrate the problem

this is the mesh as it should appear [in object mode]

when I switch to texture paint mode it appears like this

rotating around the mesh causes other areas to become visible or the whole mesh to disappear

any help or ideas would be greatly appreciated!!

Start clipping value too high.